SB 7.10.62
vatsas casit tada brahma
svayam visnur ayam hi gauh
pravisya tripuram kale
rasa-kupamrtam papau
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Then Lord Brahma became a calf and Lord Visnu a cow, and at noon they entered the residences and drank all the nectar in the well.