2.46 If there be no need for the infinite results of all the rites and duties mentioned in the Vedas, then why should they be performed as a dedication to God? Listen to the answer being given:
In the world, yavan, whatever; arthah, utility, use, like bathing, drinking, etc.; one has udapane, in a well, pond and other numerous limited reservoirs; all that, indeed, is achieved, i.e. all those needs are fulfilled to that very extent; sampluhtodake, when there is a flood; sarvatah, all arount. In a similar manner, whatever utility, result of action, there is sarvesu, in all; the vedesu, Vedas, i.e. in the rites and duties mentioned in the Vedas; all that utility is achieved, i.e. gets fulfilled; tavan, to that very extent; in that result of realization which comes brahmanasya, to a Brahmana, a sannyasin; vijanatah, who knows the Reality that is the supreme Goal  that result being comparable to the flood all around. For there is the Upanisadic text, '৷৷.so all virtuous deeds performed by people get included in this one৷৷.who knows what he (Raikva) knows৷৷.' (Ch. 4.1.4). The Lord also will say, 'all actions in their totality culminate in Knowledge' (4.33). [The Commentators otation from the Ch. relates to meditation on the alified Brahman. Lest it be concluded that the present verse relates to knowledge of the alified Brahman only, he otes again from the Gita toshow that the conclusion holds good in the case of knowledge of the absolute Brahman as well.]
Therefore, before one attains the fitness for steadfastness in Knowledge, rites and duties, even though they have (limited) utility as that of a well, pond, etc., have to be undertaken by one who is fit for rites and duties.