Which Hindu scriptures discuss the Sati practice?

Question

My teacher said that the Sati practice was not actually a common practice and does not belong to our dharma. Vedic Religion was there from around 500 BC but Sati started from around 4th century (I forgot the number but I guess it was 4th). She also mentioned that at that time widows were seen in bad light and usually after wars (like in Rajput wars) widows were tortured physically and sexually. Also widows were expected to marry their husbands' younger brother. So the widow will voluntarily jump in to fire of her dead husband.

But I also saw someone commenting:

Sati is not a questionable practice. It is the greatest display of chastity a woman can show toward her husband, and since chastity comes from the mind, it is only true if it is voluntary. It is also religious, because it is accepted by shastras and they mention phalan (great rewards) for this act. It is not 'merely cultural'

So my question is where in our texts is Sati mentioned? Also, except sati devi, is there anyone who performed sati?

NOTE

This is not a dup. of the other question What is the truth behind the practice of Sati? How is it related to Hinduism? There, the asker wants to know the truth behind Sati system. The top-voted answer there doesn't cite any sources and goes on to say that Sati is a cultural practice and not a religious one. This question however is looking for scriptural sanction for Sati and some real examples.

Answer 1

Only a Pativrata alone can enter the pyre upon the death of her husband. That too, if she has young children, or she is pregnant, or she is menstruating, even a Pativrata too cannot undergo Sati.

I will provide verses from scriptures which discuss Sati practice:

Parasara Smriti 4.32

If a woman follows her departed lord, by burning herself on the same funeral pyre, she will dwell in heaven for as many years as there are hairs on the human frame, — which reach the number of three crores and a half.

Vishnu Dharma Sutra 25.14

After the death of her husband, to preserve her chastity, or to ascend the pile after him.

Agni Purana 222.223

The widow who practices self-control and austerities after the death of her husband, goes to heaven…the widow who burns herself on the same funeral pire wth her husband also goes to heaven.

Answer 2

Where in our texts is satī mentioned? Besides Satī devī, are there others who performed satī?

First off, Satī's jumping into the sacrificial fire doesn't count as satī because her husband Śiva was alive at that point.

Here's a couple of instances from the Itihāsas, check Wikipedia for more.

1. In Vālmīki Rāmāyaṇa (Uttara-kāṇḍa), we find Vedavatī's mother ascend the funeral pyre of her dead father, Kuśadhvaja.

   Chapter 7 [Uttara-kāṇḍa] – Sarga 17

   O king! After this, the mighty-armed one wandered around on earth. Ravana reached a forest in the Himalayas and roamed around there. There, he saw a maiden with matted hair, clad in black antelope skin. Like a goddess, she was observing noble rituals and performing austerities. He saw the beautiful maiden who was observing that extremely great vow. His soul was confused because of desire. He smiled and asked her, "O fortunate one! Acting against your youth, why are you behaving in this way? This kind of reaction is not right for someone who possesses your beauty. O fortunate one! Whose daughter are you? O unblemished one! Who is your husband? I am asking you. Tell me. Why are you performing austerities in this secluded place?" The maiden was thus asked by the ignoble rakshasa. The store of austerities followed the due rituals of hospitality and said, "A brahmana rishi who follows dharma is my father and his name is Kushadhvaja. The prosperous one is Brihaspati's son and he is like Brihaspati in intelligence. The great-souled one always practises the Vedas. I have been born as his eloquent daughter. I am known by the name of Vedavati. Desiring to accept me as a bride, gods, gandharvas, yakshas, rakshasas and serpents have gone to my father. O lord of the rakshasas! However, my father did not bestow me on them. O mighty-armed one! I will tell you the reason. Listen. My father intended that Vishnu, supreme among the gods and the lord of the three worlds, should be his son-in-law. My father did not want anyone else. There was a king of the daityas, named Shambhu, and he was insolent because of his strength. On hearing that the one with dharma in his soul wished to bestow me in this way, he was filled with rage. While my father was asleep during the night, the evil one killed him. My distressed mother embraced my father's head. With him, the immensely fortunate one entered the funeral pyre. My desire is to make my father's wish about Narayana come true. That is the virtuous intention in my heart. Even if I have to die, I will accomplish my father's wish. I have taken that pledge and am therefore undertaking these pervasive austerities. O bull among rakshasas! I have thus told you everything. Know that I have resorted to this dharma because I desire Narayana as my husband. O king! O Poulastya's descendant! I know about you. Because of my austerities, I can know everything that goes on in the three worlds." At this, Ravana spoke to the maiden who was observing this extremely great vow.

   ...

   (The Valmiki Ramayana: Volume 3 by Bibek Debroy)

2. In Mahābhārata, we see Mādrī doing the same at the funeral of her husband, Pāṇḍu.

   Adi Parva (Sambhava Parva) – Chapter 90

   ...

   'Pandu had two gems among women as his wives – Kunti and Madri. One day, Pandu went out for a hunt and saw a rishi, in the form of a stag, uniting with a doe. He shot him with an arrow while he was still mounted on the doe, in a state of lust, but without his desire having been satiated. Wounded by the arrow, he told Pandu, "You follow dharma and you know the pleasure that comes from satisfaction of desire. But you have killed me before my desire was satiated. Therefore, you will also be united with the five elements in a similar state, before your desire is satiated." Pandu paled on hearing this curse and from that time, stayed away from uniting with his wives. He told them, "This is the result of my own folly. But I have heard that in the hereafter there are no worlds for those who are childless." Therefore, he asked Kunti to bear children for him and accordingly Kunti bore children. Through Dharma, Yudhishthira. Through Marut, Bhima. Through Shakra, Arjuna. Pandu was pleased and said, "Your co-wife doesn't have children either. Let the right offspring also be fathered on her." Kunti agreed and Nakula and Sahadeva were then fathered on Madri through the Ashvins. One day, Pandu saw Madri dressed in her ornaments and his desire was stirred. But he died as soon as he touched her. Then Madri ascended the funeral pyre with him, requesting Kunti to affectionately rear the twins.

   'Later, ascetics took the five Pandavas and Kunti to Hastinapura and introduced them to Bhishma and Vidura. An attempt was made to burn them in the house of lac, but this failed, because of Vidura's counsel. After this, Hidimba was killed and they went to a place named Ekachakra. In Ekachakra, they killed a rakshasa named Baka and then went to the capital of Panchala. Thereafter, ...

   (The Mahabharata: Volume 1 by Bibek Debroy)