Verse 2.21.3

तदेष श्लोको यानि पञ्चधा त्रीणी त्रीणि तेभ्यो न ज्यायः परमन्यदस्ति ॥ २.२१.३ ॥

tadeṣa śloko yāni pañcadhā trīṇī trīṇi tebhyo na jyāyaḥ paramanyadasti || 2.21.3 ||

3. Here is a verse in this connection: There are five parts of Sāma, and each of these is divided into three parts. There is nothing higher than these [fifteen forms of Sāma].

Word-for-word explanation:

Tat eṣaḥ ślokaḥ, here is a verse on the subject; yāni pañcadhā, that [Sāma] which is divided into five parts [hiṃkāra, prastāva, udgītha, pratihāra, and nidhana]; trīṇi trīṇi, each again divided into three parts [such as hiṃkāra representing the three Vedas]; tebhyaḥ jyāyaḥ param anyat na asti, there is nothing higher than these.

Commentary:

So long we have discussed the five forms of the Sāma: hiṃkāra, prastāva, udgītha, pratihāra, and nidhana. In the present verse the Upaniṣad says that each of these five can be divided further into three: hiṃkāra as the Ṛk, the Yajuḥ, and the Sāma; prastāva as the earth, the intermediate space (between the earth and heaven), and heaven; udgītha as fire, air, and the sun; pratihāra as the stars, the birds, and the rays; and nidhana as the snakes, the celestial musicians, and the ancestors.

It is Sāma which is manifest in all of these fifteen