Sutra 3.4.28

28. And there is permission of all food in the case of danger of life; on account of this being seen.

In the meditation on prāṇa, according to the Vājasaneyins and the Chāndogas, there is a statement as to all food being allowed to him who knows the prāṇa. 'By him there is nothing eaten that is not food' (Bṛ. Up. VI, 1, 14; and so on). A doubt here arises whether this permission of all food is valid for him who possesses the knowledge of prāṇa, in all circumstances, or only in the case of life being in danger.—The Pūrvapakshin holds the former view, on account of no special conditions being stated in the text.—This the Sūtra sets aside 'in the case of danger to life'; for the reason that, as the text shows, the eating of food of all kinds is permitted even for those who know Brahman itself—the knowledge of which of course is higher than that of prāṇa—only when their life is in danger. The text alluded to is the one telling how Ushasta Cākrāyaṇa, who was well versed in the knowledge of Brahman, once, when in great distress, ate unlawful food. We therefore conclude that what the text says as to all food being lawful for him who knows prāṇa, can refer only to occasions when food of any kind must be eaten in order to preserve life.