Srimad-Bhagavatam: Canto 7 - Chapter 1 - Verse 62
Sanskrit:
वत्सश्चासीत्तदा ब्रह्मा स्वयं विष्णुरयं हि गौ: ।प्रविश्य त्रिपुरं काले रसकूपामृतं पपौ ॥ ६२ ॥
ITRANS:
vatsaś cāsīt tadā brahmāsvayaṁ viṣṇur ayaṁ hi gauḥpraviśya tripuraṁ kālerasa-kūpāmṛtaṁ papau
Translation:
Then Lord Brahmā became a calf and Lord Viṣṇu a cow, and at noon they entered the residences and drank all the nectar in the well.