Taittirīyopaniṣat 03.11

Let him not refuse anyone who seeks to dwell (with him). That is the vow. Therefore, by whatever means one may obtain much food, people say: “Food should be served to him.” Indeed, this is success attained by serving the mouth with regard to food; through (serving) the mouth, he succeeds in attaining the food. Indeed, for him who knows thus: middle is the success attained regarding the food for one who is middle-aged; feet is the success attained regarding the food for one who is aged.

Taittirīya Bhāshya 03.11

Lord Vishnu, in the form of fire, water, earth, and ether, resides in food. He abides as both the enjoyer and the enjoyed, playing by himself. Mere enjoyability does not imply any inferiority in Him anywhere. Hence, never to disrespect the food, and never to say 'not welcome' to guests, are the two vows to be practiced.

"... For the sake of knowledge, when one comes with the desire to reside, one should not say 'not welcomed'; this is the vow of the wise.

He, Lord Viṣṇu, is known as 'Earth' because of his vastness; as 'Prāṇa', by virtue of supreme bliss and strength; as 'ether', by knowing all, as he is the knower of everything.

He is known as 'Śara', among the embodied, and is known through the impulse. By these four, the Lord manifests through forms and the fourfold selves.

He abides as both the enjoyer and the enjoyed, playing by himself. Mere enjoyability does not imply any inferiority in him anywhere.

A husband is not to be treated as an object of enjoyment by the wife, for otherwise he would become inferior. In the same way, Lord Viṣṇu remains undifferentiated in all beings.

He always plays among forms, being both the enjoyer and the enjoyed by desire; one should never blame him who is called food, but should always greatly respect him.

Thus, if one desires happiness, these two vows must indeed be observed; by whatever means or method, as much as possible, and one should worship Lord Janardana (Krishna).

Having known thus, one should always attain (him) by the activities of mind, speech, and body. He who thus worships, for him Hari himself is called Anna (food).

The wise who are well-established indeed say 'accomplished'; for one whose Brahman is perfectly attained before, by him it is obtained further on.

If one attains realization in the middle of life, the liberated perceive the centre. If one realizes in old age, the liberated perceives the feet.

In youth, one sees only the radiant circle as another limb of Viṣṇu. This should be understood from the outset for the complete vision."