These three are the shoulders (supports) of Dharma in all the stages of life, i.e. study, yajna -‘the action portion’ and charitable gifts. In the first stage theBrahmacharya lives in the family of the preceptor doing austerities, acquiring good education and performing the dharma. 

The second is the stage of the householder. In the third, the dweller in the forest, keeping down his body as much as possible, keeping his mind involved in thought and retiring in a solitary place, should determine what is true and what is false. All of these Ashramas are the seats of merit and abodes of happiness.

They are called ashramas (resting places) because meritorious acts are performed in them. Acquiring learning and making oneself sure about God and thedharma in the Brahmacharya ashrama, putting to practice what one has learned and increasing and improving one’s knowledge in the Grihasthashrama and then resorting to a lonely palace in the forest and there determining what things and acts are right and what are wrong and finishing the (duties of)Vanaprasthashrama one should become a Sanyasi.

There is a difference of opinion as to when a man should become a Sanyasi. Some say that one should become a householder after finishing theBrahmacharya ashrama and then should go to dwell in the forest and then one should become a Sanyasi. According to the others, one may enter Sanyasaafter finishing

the duties of a householder without entering into Vanaprasthashrama. There are yet others who say that one may become a Sanyasi after duly fulfilling he vows of Brahmacharya ashrama and without entering into Grihastha and Vanaprastha ashramas. The inference is that the performance of the Brahmacharya ashrama is compulsory; because the other ashramas cannot come into existence without the Brahmacharyashrama. (Chhandogya II -23), 1 and 2.