SB 9.18.44
uttamas cintitam kuryat
prokta-kari tu madhyamah
adhamo ’sraddhaya kuryad
akartoccaritam pituh
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
A son who acts by anticipating what his father wants him to do is first class, one who acts upon receiving his father’s order is second class, and one who executes his father’s order irreverently is third class. But a son who refuses his father’s order is like his father’s stool.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Puru, Yayati’s last son, immediately accepted his father’s proposal, for although he was the youngest, he was very qualified. Puru thought, “I should have accepted my father’s proposal before he asked, but I did not. Therefore I am not a first-class son. I am second class. But I do not wish to become the lowest type of son, who is compared to his father’s stool.” One Indian poet has spoken of putra and mutra. Putra means “son,” and mutra means “urine.” Both a son and urine come from the same genitals. If a son is an obedient devotee of the Lord he is called putra, or a real son; otherwise, if he is not learned and is not a devotee, a son is nothing better than urine.