Canto 2 -
Ayodhyā-kāṇḍa
Chapter 26: Rāma Meets Sītā and Instructs Her
Text 2.26.29

याते च मयि कल्याणि वनं मुनिनिषेवितम्।
व्रतोपवासपरया भवितव्यं त्वयानघे॥

yāte ca mayi kalyāṇi vanaṁ muni-niṣevitam
vratopavāsa-parayā bhavitavyaṁ tvayānaghe

yāte ca = go; mayi = when I; kalyāṇi = O auspicious; vanam = to the forest; muni-niṣevitam = resorted to by the sages; vrata-upavāsa-parayā = absorbed in vows and fasts; bhavitavyam = should become; tvayā = you; anaghe = and sinless lady.

O auspicious and sinless lady, when I go to the forest resorted to by the sages, you should become absorbed in vows and fasts.

NOTE. In the Fourth Chapter of Bhagavad-gītā, Lord Kṛṣṇa explains that the prescribed activities of Vedic culture are factually various forms of sacrifices. Among them, one such variety is called tapo-yajña, “the sacrifice of austerities” where one takes up vows and fasts. And the goal of these sacrifices are set out by the Lord Himself thus:

sarve ’py ete yajña-vido yajña-kṣapita-kalmaṣāḥ
yajña-śiṣṭāmṛta-bhujo yānti brahma sanātanam

“All these performers who know the meaning of sacrifice become cleansed of sinful reactions, and, having tasted the nectar of the results of sacrifices, they advance toward the supreme eternal atmosphere.” (Bhagavad-gītā 4.30)