Sutra 3.1.5

5. Should it be said, on account of absence of mention in the first (reply); we say no, for just that (is meant), on the ground of fitness.

An objection is raised to the conclusion arrived at under III, 1, 1; on the ground that in the first oblation, described in Ch. Up. V, 4, 2, as being made into the heavenly world, water is not mentioned at all as the thing offered. The text says, 'on that altar the gods offer śraddhā'; and by śraddhā (belief) everybody understands a certain activity of mind. Water therefore is not the thing offered.—Not so, we reply. It is nothing else but water, which there is called śraddhā. For thus only question and answer have a sense. For the question is, 'Do you know why in the fifth libation water is called man?' and at the outset of the reply śraddhā is mentioned as constituting the oblation made into the heavenly world viewed as a fire. If here the word śraddhā did not denote water, question and answer would refer to different topics, and there would be no connexion. The form in which the final statement is introduced (iti tu pañcamyām, etc., 'but thus in the fifth oblation,' etc.), moreover, also intimates that śraddhā means water. The word 'iti,' thus, here intimates that the answer is meant to dispose of the question, 'Do you know how?' etc. Śraddhā becomes moon, rain, food, seed, embryo in succession, and thus the water comes to be called man. Moreover, the word śraddhā is actually used in the Veda in the sense of 'water'; 'he carries water, śraddhā indeed is water' (Taitt. Saṃh. I, 6, 8, 1). Aad what the text says as to king Soma (the moon) originating from śraddhā when offered, also shows that śraddhā must mean water.