SB 3.13.7

tvam ekaḥ sarva-bhūtānāṁ
 janma-kṛd vṛttidaḥ pitā
tathāpi naḥ prajānāṁ te
 śuśrūṣā kena vā bhavet
Synonyms: 
tvam — you; ekaḥ — one; sarva — all; bhūtānām — living entities; janma-kṛt — progenitor; vṛtti-daḥ — source of subsistence; pitā — the father; tathā api — yet; naḥ — ourselves; prajānām — of all who are born; te — of you; śuśrūṣā — service; kena — how; — either; bhavet — may be possible.
Translation: 
You are the father of all living entities and the source of their subsistence because they are all born of you. Please order us how we may be able to render service unto you.
Purport: 

A son’s duty is not only to make the father the source of supply for all his needs, but also, when he is grown up, to render service unto him. That is the law of creation beginning from the time of Brahmā. A father’s duty is to bring up the son until he is grown, and when the son is grown up, it is his duty to render service unto the father.