SB 7.12.16
evam vidho brahmacari
vanaprastho yatir grhi
caran vidita-vijñanah
param brahmadhigacchati
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
By practicing in this way, whether one be in the brahmacari-asrama, grhastha-asrama, vanaprastha-asrama or sannyasa-asrama, one must always realize the all-pervading presence of the Supreme Lord, for in this way it is possible to understand the Absolute Truth.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
This is the beginning of self-realization. One must first understand how Brahman is present everywhere and how He is acting. This education is called brahma-jijñasa and is the real concern of human life. Without such knowledge, one cannot claim to be a human being; rather, he remains in the animal kingdom. As it is said, sa eva go-kharah: without such knowledge, one is no better than a cow or an ass.