Srimad Bhagavatam Canto 06, Chapter 07, Text 28

SB 6.7.28

putranam hi paro dharmah
 pitr-susrusanam satam
api putravatam brahman
 kim uta brahmacarinam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
O brahmana, the highest duty of a son, even though he has sons of his own, is to serve his parents, and what to speak of a son who is a brahmacari?
Srimad Bhagavatam Canto 06, Chapter 07, Text 27
Srimad Bhagavatam Canto 06, Chapter 07, Text 29-30