SB 3.13.7
tvam ekah sarva-bhutanam
janma-krd vrttidah pita
tathapi nah prajanam te
susrusa kena va bhavet
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
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 by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
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 Brahma. 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.