SB 8.16.50

trayodaśyām atho viṣṇoḥ
 snapanaṁ pañcakair vibhoḥ
kārayec chāstra-dṛṣṭena
 vidhinā vidhi-kovidaiḥ
Word for word: 
trayodaśyām — on the thirteenth day of the moon; atho — thereafter; viṣṇoḥ — of Lord Viṣṇu; snapanam — bathing; pañcakaiḥ — by pañcāmṛta, five substances; vibhoḥ — the Lord; kārayet — one should execute; śāstra-dṛṣṭena — enjoined in the scripture; vidhinā — under regulative principles; vidhi-kovidaiḥ — assisted by the priests who know the regulative principles.
Translation: 
Thereafter, following the directions of the śāstra with help from brāhmaṇas who know the śāstra, on the thirteenth day of the moon one should bathe Lord Viṣṇu with five substances [milk, yogurt, ghee, sugar and honey].