Verse 2.21.4

यस्तद्वेद स वेद सर्वं सर्वा दिशो बलिमस्मै हरन्ति सर्वमस्मीत्युपासित तद्व्रतं तद्व्रतम् ॥ २.२१.४ ॥
॥ इति एकविंशः खण्डः ॥

yastadveda sa veda sarvaṃ sarvā diśo balimasmai haranti sarvamasmītyupāsita tadvrataṃ tadvratam || 2.21.4 ||
|| iti ekaviṃśaḥ khaṇḍaḥ ||

4. He who knows Sāma knows everything, and gifts come to him from all quarters. His vow will be to constantly say to himself, ‘I am one with all’.

Word-for-word explanation:

Yaḥ tat veda, he who knows that [Sāma]; saḥ veda sarvam, he knows all; sarvāḥ diśaḥ, all the quarters; balim, gifts; asmai, for him; haranti, bring; sarvam asmi, I am all; iti upāsīta, this is how he will meditate; tat vratam tat vratam, this is his vow, this is his vow. Iti ekaviṃśaḥ khaṇḍaḥ, here ends the twenty-first section.

Commentary:

Sāma is the inmost being of all, and he who knows it as such becomes like Sāma—that is, he becomes the inmost being of all, and he knows everything. People come from everywhere with gifts to show him their respect.

‘I am Sāma, the inmost being of all’—this is how Sāma is to be worshipped. One should constantly repeat this to oneself. In fact, it should be treated as a vow.

Section Twenty-Two