Srimad Bhagavatam Canto 09, Chapter 07, Text 10

SB 9.7.10

jatah suto hy anenanga
 mam yajasveti so ’bravit
yada pasur nirdasah syad
 atha medhyo bhaved iti
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Thereafter, when the child was born, Varuna approached Hariscandra and said, “Now you have a son. With this son you can offer me a sacrifice.” In answer to this, Hariscandra said, “After ten days have passed since an animal’s birth, the animal becomes fit to be sacrificed.”
Srimad Bhagavatam Canto 09, Chapter 07, Text 09
Srimad Bhagavatam Canto 09, Chapter 07, Text 11