SB 9.7.10

jātaḥ suto hy anenāṅga
 māṁ yajasveti so ’bravīt
yadā paśur nirdaśaḥ syād
 atha medhyo bhaved iti
Synonyms: 
jātaḥ — has been born; sutaḥ — a son; hi — indeed; anena — by this son; aṅga — O Hariścandra; mām — unto me; yajasva — offer sacrifice; iti — thus; saḥ — he, Varuṇa; abravīt — said; yadā — when; paśuḥ — an animal; nirdaśaḥ — has passed ten days; syāt — should become; atha — then; medhyaḥ — suitable for offering in sacrifice; bhavet — becomes; iti — thus (Hariścandra said).
Translation: 
Thereafter, when the child was born, Varuṇa approached Hariścandra and said, “Now you have a son. With this son you can offer me a sacrifice.” In answer to this, Hariścandra said, “After ten days have passed since an animal’s birth, the animal becomes fit to be sacrificed.”