SB 10.84.39
rnais tribhir dvijo jato
devarsi-pitrnam prabho
yajñadhyayana-putrais tany
anistirya tyajan patet
Translation:
Dear Prabhu, a member of the twice-born classes is born with three kinds of debts — those owed to the demigods, to the sages and to his forefathers. If he leaves his body without first liquidating these debts by performing sacrifice, studying the scriptures and begetting children, he will fall down into a hellish condition.
Purport:
Concerning the special obligations of a brahmana, the sruti states, jayamano vai brahmanas tribhir rnavañ jayate brahmacaryena rsibhyo yajñena devebhyah prajaya pitrbhyah: “Whenever a brahmana takes birth, three debts are born along with him. He can pay his debt to the sages by celibacy, his debt to the demigods by sacrifice, and his debt to his forefathers by begetting children.”