I know the injunction for Dvijas to do Sandhyavandanam is found in the Manusmriti, but where is this injunction found in the Vedas?
The Gayatri mantra is found in the Vedas, but where is the injunction to do Sandhyavandanam found in the Vedas (including Samhitas, Brahmanas, Aranyakas, Upanishads)?
The oldest extant Vedic scripture to mandate Sandhyāvandana is probably the Āśvalāyana Gṛhyasūtra (attached to Ṛgveda):
Adhyāya III, Kaṇḍikā 7
If the sun sets while he is sleeping without being sick, he should spend the rest of the night keeping silence, without sitting down, and should worship the sun (when it rises) with the five (verses), 'The light, O sun, by which thou destroyest darkness' (Rig-veda X, 37, 4 seq.).
If (the sun) rises (while he is sleeping without being sick), being fatigued without having done any work, or having done work that is not becoming, he should keep silence, &c., as before, and perform his worship (to the sun) with the following four (verses, Rig-veda X, 37, 9 seq.).
Invested with the sacrificial cord, constantly fulfilling the prescribed duties regarding the use of water, he should perform the Sandhyā (or twilight devotion), observing silence.
In the evening he should, turning his face to the north-west, to the region between the chief (west) point and the intermediate (north-western) point (of the horizon), murmur the Sāvitrī, (beginning) when the sun is half set, until the stars appear.
In the same way in the morning—
Standing, with his face turned to the east, until the disk (of the sun) appears.
If a dove flies against his house or towards it, he should sacrifice with (the hymn), 'O gods, the dove' (Rig-veda X, 165), verse by verse, or should murmur (that hymn).
'We have thee, O Lord of the path' (Rig-veda VI, 53)—if he is going out for doing some business.
'Bring us together, Pūṣan, with a knowing one' (Rig-Veda VI, 54)—if he wishes to find something lost, or if he has strayed.
'Journey over the ways, Pūṣan' (Rig-veda I, 42)—if he is going out on a long or dangerous way.
Although not injunctive, Ganganath Jha's notes on Manu 2.101 points to a verse from the Taittirīya-Brāhmaṇa that extols Sandhyāvandana:
Taittirīya-Brāhmaṇa (Parāśaramādhava, p. 268).—‘Meditating upon the sun, rising and setting, if the learned Brāhmaṇa offer the Prayers, he obtains all that is good.’
The Baudhāyana Dharmasūtra (Kṛsna Yajurveda) has a similar verse sourced from the Vedas:
Praśna II, Adhyāya 4, Kaṇḍikā 7
- Now, therefore, we will declare the rule for (performing) the twilight devotions.
...
- It is declared in the Veda, 'A Brāhmaṇa who in this same manner daily worships in the twilight, both at morn and at eve and, being sanctified by the Brahman, becoming one with the Brahman, and resplendent through the Brahman, follows the rules of the Śāstra, gains the heaven of Brahman.'
Rig Veda IV.54.6 says as follows:
ये ते॒ त्रिरह॑न् त्सवितः स॒वासो॑ दि॒वेदि॑वे॒ सौभ॑गमासु॒वन्ति॑ । इन्द्रो॒ द्यावा॑पृथि॒वी सिन्धु॑र॒द्भिरा॑दि॒त्यैर्नो॒ अदि॑ति॒: शर्म॑ यंसत् ॥६॥
O Savitar, as three times a day your impulsions impel good fortune day after day, Indra, Heaven and Earth, the Sindhu with her waters, Aditi with the Ādityas, will extend shelter to us.
So adoring Savitar, while offering oblations , has roots in Rig Veda.
