Bhashya
आपो वास इति ; आपः भक्ष्यमाणाः वासःस्थानीयास्तव ।अत्र च प्राणस्य आपो वास इत्येतद्दर्शनं विधीयते ; न तु वासःकार्ये आपो विनियोक्तुं शक्याः ; तस्मात् यथाप्राप्ते अब्भक्षणे दर्शनमात्रं कर्तव्यम् ।न ह वै अस्य सर्वं प्राणस्यान्नमित्येवंविदः अनन्नम् अनदनीयं जग्धं भुक्तं न भवति ह ; यद्यपि अनेन अनदनीयं भुक्तम्, अदनीयमेव भुक्तं स्यात्, न तु तत्कृतदोषेण लिप्यते— इत्येतत् विद्यास्तुतिरित्यावोचाम ।तथा न अनन्नं प्रतिगृहीतम् ; यद्यपि अप्रतिग्राह्यंता आचमनस्य स्यान्; न च कार्यद्वयम् आचमनस्य एकस्ययुक्तम्; यदि प्रायत्यार्थम्, न अनग्नतार्थम्; अथ अनग्न-तार्थम्, न प्रायत्यार्थम्; यस्मादेवम्, तस्मात् द्वितीयम् आ-चमनान्तरं प्राणस्यानग्नताकरणाय भवतु- न, क्रियाद्वि-त्वोपपत्तेः; द्वे ह्येते किये, भोक्ष्यमाणस्य भुक्तवतश्च यत्आचमनं स्मृतिविहितम्, तत् प्रायत्यार्थं भवति क्रियामा-त्रमेव; न तु तत्र प्रायत्यं दर्शनादि अपेक्ष्यते, तत्र चआचमनाङ्गभूतास्वप्सु वासोविज्ञानं प्राणस्य इतिकर्तव्यतयाचोद्यते, न तु तस्मिन्क्रियमाणे आचमनस्य प्रायत्यार्थताबाध्यते, क्रियान्तरत्वादाचमनस्य ।तस्मात् भोक्ष्यमाणस्यभुक्तवतश्च यत् आचमनम्, तत्र आपो वासः प्राणस्येतिदर्शनमात्रं विधीयते, अप्राप्तत्वादन्यतः ॥
In plain words
'Water is a garment' — when you drink it, water plays the part of clothing for you, prana. Here too, what's being taught is only a way of seeing: water as prana's garment. Water obviously can't actually function as clothing, so all that's asked, when you drink water as you normally would, is to hold that vision in mind. As already said: for someone who knows that everything is prana's food, eating something inedible doesn't make him a transgressor — he still eats what's technically not-food, but he isn't stained by the fault of it. That was praise for the teaching, not a license. In the same way, water isn't wrongly 'accepted' as a gift by drinking it. And a single ritual sipping can't be doing two jobs at once — either it's for purity or it's for removing a kind of ritual 'nakedness,' not both. So don't imagine a second sipping is needed to clothe prana: two acts are already built into the practice, one before eating and one after, both prescribed by tradition purely for purity, nothing more. No visible cleanliness is required there. What is required, in those very waters used for sipping, is simply remembering: this water is prana's garment. That doesn't cancel the sipping's real purpose of purity — recognizing water as a garment is a separate act entirely. So in both sippings, before the meal and after, all that's enjoined is this one vision, water as prana's garment, because there was nowhere else you could have learned it.
Close to the Sanskrit
'Water is a garment' — waters, being drunk, stand in the place of a garment for you. Here too, the vision that water, belonging to prāṇa, is a garment is enjoined; but water cannot actually be employed for the function a garment serves; therefore, on the ordinary occasion of drinking water, only the vision is to be performed. It is not that, for one who knows thus that everything is prāṇa's food, non-food — the inedible — eaten becomes something [wrongly] eaten; even though the inedible is eaten by him, it would be as if the edible alone were eaten, but he is not tainted by the fault caused by it — this point, we have already stated, is a praise of the teaching. Likewise, non-food is not [wrongly] accepted as a gift; even though, if water were unacceptable, that would belong to the sipping-rite — nor is a double function proper for the single sipping-rite; if it is for the sake of purity, it is not for the sake of removing 'nakedness'; if it is for the sake of removing 'nakedness', it is not for the sake of purity; since this is so, therefore [one might propose that] a second act of sipping should exist, for effecting prāṇa's 'non-nakedness' — no, because a duality of acts is already accounted for; these are indeed two acts: for one about to eat and for one who has eaten, the sipping enjoined by the smṛti texts is for the sake of purity, being a mere act alone; there, purity by way of seeing and the like is not required; and there, in the waters forming part of the sipping-rite, the recognition that water is a garment for prāṇa is prescribed as one detail of how the rite is performed — but it is not that, when that recognition is being performed, the sipping-rite's purpose of purity is thereby cancelled, since it is a separate act from the sipping-rite itself. Therefore, in the sipping done by one about to eat and one who has eaten, there the vision alone that water is prāṇa's garment is enjoined, because it could not have been known from any other source.