What is the reason for Lord Rama to ask Mother Sita to give Agni Pariksha? What do the scriptures say about this?
In this chapter of the Yuddha Kanda of the Ramayana, Rama explains why he made Sita walk through fire, despite having complete trust in her:
Seetha certainly deserves this pure factory ordeal in the eyes of the people in as much as this blessed woman had resided for a long time indeed in the gynaecium of Ravana. The world would chatter against me, saying that Rama, the son of Dasaratha, was really foolish and that his mind was dominated by lust, if I accept Seetha without examining her with regard to her chastity.
I also know that Seetha, the daughter of Janaka, who ever revolves in my mind, is undivided in her affection to me. Ravana could not violate this wide-eyed woman, protected as she was by her own splendour, any more than an ocean would transgress its bounds.
In order to convince the three worlds, I, whose refugee is truth, ignored Seetha while she was entering the fire. The evil-minded Ravana was not able to lay his violent hands, even in thought, o the unobtainable Seetha, who was blazing like a flaming tongue of fire. This auspicious woman could not give way to the sovereignty, existing in the gynaecium of Ravana, in as much as Seetha is not different from me, even as sunlight is not different from the sun. Seetha, the daughter of Janaka, is completely pure in her character, in all the three worlds and can no longer be renounced by me, as a good name cannot be cast aside by a prudent man. The salutary advice of you all, the affectionate guardians of the world, who are saying what is conducive to our good, must be certainly carried out by me.
So it was done in order to demonstrate to the rest of the world that Rama wasn't taking in an unfaithful wife, even though Rama personally knew she was faithful.
Of course, this still wasn't enough to make the people of Ayodhya believe that Sita had been faithful, which is what ultimately led to Sita's exile.
By the way, on a side note according to the Skanda Purana, it is Vedavati, not the real Sita who goes into the fire, as I discuss in my answer here.
Seeta parityaga (Disowning) episode - a character assassination
The Seeta parityaga (Disowning of Seeta), Seeta Agnipravesha, arrival of all GODs and Sri Rama accepting Seeta episodes were described in the Sargas 115 to 118 of Yuddha Kanda of Srimad Ramayana.
Sri Rama sends Vibhishana to bring Seetha to his presence. Vibhishana brings Seetha to Sri Rama's presence.
Sri Rama informs Seetha that the dishonour meted out to him and the wrong done to her by Ravana have been wiped off, by his victory over the enemy with the assistance of Sri Hanuma, Sugreeva and Vibhishana.
However, regarding with suspicion on the character of Seetha, Sri Rama disowns her and asks her to seek shelter elsewhere.
Seetha gives a taunting reply to Sri Rama, saying that why she was not abandoned by the latter, even at the time when Sri Hanuma came to see her in Lanka.
Then, Seetha requests Lakshmana to prepare a pile of fire for her to enter. When Lakshmana prepares a pyre, Seetha prays the fire-god and enters into it, in order to prove her conjugal fidelity.
Lord Brahma, Lord Shiva and other gods reach that place and eulogise Sri Rama as the incarnation of Lord Vishnu and Seeta as Adilakshmi.
ततो वैश्रवणो राजा यमश्च पृभिः सह | सहस्राक्षश्च देवेशो वरुणश्च जलेश्वरः || षड्र्धनयनः श्रीमान् महादेवो वृषध्वजः | कर्ता सर्वस्य लोकस्य ब्रह्मा ब्रह्मविदां वरः || एते सर्वे समागम्य विमानैः सूर्यसंनिभैः | आगम्य नगरीं लङ्कामभिजग्मुश्च राघवम् || (Yuddha Kanda 117 Sarga 2 - 4 Slokas)
"Thereupon, Kubera the King of Yakshas, Yama the lord of death together with the deceased ancestors, Indra the lord of celestials Varuna the lord of waters, the illustrious Shiva the great deity who bears the device of a bull as his banner and having three eyes, Brahma the creator of all the worlds and the best among the knowers of sacred knowledge all these together reaching the City of Lanka in aerial cars, shining like the sun approached Rama."
After lengthy dialogue, Lord Brahma requests Sri Rama to take back Sita.
विशुद्धभावां निष्पापां प्रतिगृह्णीष्व मैथिलीम् | न किंचिरभिधातव्या अहमाज्ञापयामि ते || (Yuddha Kanda 118 Sarga 10 Sloka)
"Take back Seetha, who is sinless, with a pure character. She should not be told anything harsh. I hereby command you."
Then Sri Rama accepts Seeta since her chastity was confirmed by AGNIPARIKSHA.
अनन्यहृदयां भक्तां मचत्तपरिवर्तिनीम् | अहमप्यवगच्छामि मैथिलीं जनकात्मजाम् || (Yuddha Kanda 118 Sarga 15 Sloka)
"I also know that Seetha, the daughter of Janaka, who ever revolves in my mind, is undivided in her affection to me."
प्रत्ययार्थं तु लोकानां त्रयाणाम् सत्यसंश्रयः | उपेक्षे चापि वैदेहीं प्रविशन्तीं हुताशनम् || (Yuddha Kanda 118 Sarga 17 Sloka)
"In order to convince the three worlds, I, whose refugee is truth, ignored Seetha while she was entering the fire."
The episode of Seeta parityaga (disowning) was, in my view, not written down by Sage Valmiki but a PRAKSHIPTA (an insertion made by somebody with a view to elevating the status of Lord Vishnu to that of SARVA LOKADHIPATI at a later date) for the following reasons.
According to Srimad Ramayana, Lord Brahma was the ultimate God and the place of Vishnu was only next to Lord Indra. Shiva was only an ex-Senadhipathi
As Putrakamesthi episode was inserted to make believe the readers that Sri Rama was in fact the incarnation of Lord Vishnu, Seeta parityaga (Disowning of Seeta), Seeta Agnipravesha, episodes were inserted consciously to pave way for the arrival of all GODs and Sri Rama accepting Seeta episodes.
Hence, eulogising Sri Rama as the incarnation of Lord Vishnu and Seeta as Adilakshmi by Lord Brahma and Lord Shiva WAS DONE to elevate the status of Lord Vishnu and did not fit into Srimad Ramayana
Sri Rama always expressed his great eagerness in getting back his dear wife Seeta at the earliest. At no point of time, till his meeting with Seeta after the death of Ravana, he was depicted expressing his desire to give up Seeta as she was residing in Ravana’s house.
If Sri Rama already had a doubt of Seeta’s conjugal fidelity or he already decided to disown Seeta after killing of Ravana, he would have felt relieved with the news of death of Seeta. Instead, his immediate reaction to the news of Indrajit chopping off the head of illusionary Seeta was to faint away.
This episode alongwith the episode of abandonment of Sita in Uttara Kanda, (interpolations) left a long lasting negative impression on the character of Sri Rama as male chauvinist.
Whoever inserted Seeta parityaga (Disowning) episode" in Ramayana, for elevating the status of Vishnu, which was an epithet in Veda, as SUPREME LORD, forgot that it led to a character assassination of Sri Rama.
Technically Rama didn't ask Sita to go into the fire. It was Sita herself who wanted this ordeal.
chitaaM me kuru saumitre vyasanasyaasya bheShajam |
mithyaapavaadopahataa naahaM jiivitumutsahe
"O Lakshmana! Create a pile of fire for me, which is a remedy for this disaster. I no longer wish to survive with false blames."
The Agnipariksha was never an intention of Rama, albeit that had to be done because the Sita who was kidnapped by Ravana was no other than an illusory form of Sita called Maya Sita. This story, retold in Caitanya caritamrta 2.9.200 - 212, appears in Kurma Purana 2.34.111 - 140.
A chaste woman devoted to piety (dharma) shall always attain welfare and happiness. No man can, by any means, create discomfiture for her.
Just as in the case of Sita,1 well-known in the three worlds, as the charming and beloved wife of Rama, the son of Dasaratha, she conquered the king of Raksasas.
Urged by Kala (Death), Ravana, the king of Raksasas, desired Sita, the wide-eyed beautiful wife of Rama.
It is reported that by means of his Maya, he disguised himself (as) an ascetic and determined to abduct that beautiful lady while she was strolling (solitarily) in the tenantless forest.
The lady of pure smiles realised his intention. Remembering her husband, the son of Dasaratha, she sought refuge in the Avasathya (household) fire.
With her palms joined in devotion, Rama's wife worshipped the great Yogi (the fire-god), the destroyer (scorcher) of the worlds, as if he was her husband Rama incarnate (and prayed): Eulogy of the Fire-god.
I bow unto Krsanu (fire) of the form of Kala, of great Yogic power, the greatest riddle, the destroyer of all living beings.
I take shelter in lord Pavaka (the purifying deity), the eternal deity of universal forms, the Yogin who wears the (elephant) hide, the lord of the goblins, the Supreme god.
I resort unto the Atman of radiant blazing body abiding in the hearts of all living beings. I seek refuge in the Lord whose form is the universe, the source of all that fiery, brilliant. I resort to the fire-god, the Lord of great Yogins, the sun, the supreme god. I seek refuge in Rudra, the great swallower (destroyer), the trident-bearing Lord, the fire of the Universal destruction, the Lord of Yogins, the dispenser of fruits (in the form) of enjoyment and liberation.
I resort unto you the diverse-eyed deity with the forms of Bhuh, Bhuvah and Svah}, one who is lying hidden in the golden abode, the great one of unmeasured splendour.
I resort to Vaisvanara abiding in all living beings, the lord who conveys Havyas and Kavyas (i.e. offerings) (to gods and Pitrs). I resort to Lord Vahni.
I resort to that Supreme reality, the excellent and auspicious principle of the sun. I resort to the Agni ascending to heaven, the greatest splendour, the imperishable conveyor of oblations to gods.
After repeating (the prayer in) these eight (?) verses on Vahni, the famous wife of Rama mentally meditated on Rama and remained silent with her eyes closed.
Then out of the Avasathya (household) fire, Lord Mahesvara (the great god), the bearer of sacrificial oblations, of resplendent soul manifested himself as if burning with his own refulgence.
Desirous of getting Ravana killed he created an illusory Sita. Taking the real Sita, the beloved of Rama, the fire-god vanished there.
On seeing such a Sita (i.e. the illusory one) Ravana the lord of Raksasas, took her and went to Lanka, situated within the ocean.
After killing Ravana, Rama took Sita and (came back) accompanied by Laksmana. His mind became agitated due to suspicion.
For convincing the living beings, the illusory Sita entered the fire; immediately she was consumed by the fire.
After burning the illusory Sita, the lord fire-god of hot rays, showed the real Sita to Rama. The fire-god (the purifier) became a beloved of Devas.
Catching hold of the feet of her husband, the daughter of Janaka, the lady of beautiful middle, made obeisance to Rama on the ground.
On seeing it Rama was delighted in mind. Surprise was evident in his eyes. After bowing to the Vahni with bent head, Raghava propitiated him.
The lord spoke to Vahni: Was this fair-complexioned lady burned by you before, as she has been seen come to my side again?
Lord Fire-god, the scorcher of the worlds, spoke to the son of Dasaratha, telling him everything as it had happened in the presence of all living beings.
"This beloved of yours is highly chaste as goddess Parvati. She is the greatest favourite of the goddess whom she had propitiated by means of penance
This chaste lady of good conduct is endowed with the readiness to serve her husband like Bhavani in regard to Isvara. She was protected by me because she was desired by Ravana.
But Sita who was abducted by the lord of Raksasas was the illusory Sita created by me with a desire to get Ravana killed.
On that account, Ravana, the wicked king of the Raksasas and the destroyer of the worlds, had been killed. The Maya has also been withdrawn.
"Accept this pure Janaki at my instance. See lord Narayana your own self the source of origin and the place of everything".
After saying this, the fierce lord fire-god whose flames spread everywhere and who had faces on all sides was duly honoured by Raghava and the other people and he vanished.
Thus we see that Maya Sita was just an illusion who went back to Agnidev through the Agnipariksha while Agnidev himself brought out the real Sita to Rama. At that moment Rama (who definitely knew everything) was (just for a show to the common public) very happy and elated. The Agnipariksha was done for 2 major reasons. 1> Return of Maya Sita back to Agnidev, and 2> A foolproof convincing of the common public that Sita was not unchaste, as a disgruntled public would not be beneficial for Ram Rajya. This was a risk which Rama had taken on his own honour. While its true that people were speaking ill about Sita, they all stopped in their tracks when they witnessed the apparently "cruel" act of Rama. Everyone’s emotions are running high. They know what they have witnessed. By this time they knew Sita was pure, even purer than fire itself. Rama had achieved his motive.
It was not possible for Ravana to even touch the lotus feet of mother Sita. Sita is the mother of the universe and the supreme goddess of fortune. Nobody can touch mother Sita. In fact, a person with material senses cannot even see her. When Ravana kidnapped her, he took only her material illusionary form.
Lord Rama is the Supreme Personality and He knew everything. He was just playing the role of a human. After the agni-pariksha, He accepted the real mother Sita. He took her back to Ayodhya, where He was coronated, King. Lord Rama set very high standards for human conduct and behavior with His exemplary qualities.
See another comprehensive answer of mine about the same topic, here.
Sita was actually the daughter of Lord Agni and Mandodari. Mondodari was very beautiful and Agni got thrilled saying her beauty . In the union Sita was born However Agni promised that Sita was born to destroy Ravanas dynasty . However you will remin as virgin only . She was asked to put Sita somewhere. Manodari filled all necessary things for the child including ornaments and asked the servants to Dispose off the child at a far away place. She was thus buried in a casket at Jankas plouging field. As Janaka had no issue he was asked to plough the field . During the act the casket was retrieved and Sitha came into the hands of Janaka. As he came ploughing field which is also called Sita , she was named thus. Later she was married to Rama. When Rama went to exile in forest Lord agni came and told Rama that I will take away Sita and give you Mayua Sita, Original Sita will be returned durting Agni Pravesh. In order to get back the Original Sita the Agni Pariksha was conducted.