Brahma Sutras – According to Shankara 3-3 4-5
Topic 4 - Specializing the ‘Om’ of the Udgītha Vidyā is apt, as ‘Om’ is common to all the Vedas
व्याप्तेश्च समञ्जसम् ॥ ९ ॥
vyāpteśca samañjasam || 9 ||
vyāpteḥ—Because (Om) extends (over the whole of the Vedas); ca—and; samañjasam—is appropriate.
9. And because (Om) extends (over the whole of the Vedas), (to specialize it by the term ‘Udgītha’) is appropriate.
Since ‘Om’ is common to all the Vedas we have to understand which particular ‘Om’ is to be meditated upon.
By specifying that the ‘Om’ which is a part of the Udgītha is to be meditated upon, we learn that it is the ’Om’ of the Sāma-Veda. “Let one meditate on the syllable ‘Om’ (of) the Udgītha” (Chh. 1. 1. 1).
Topic 5 - Unity of the Prāṇa Vidyā
सर्वाभेदादन्यत्रेमे ॥ १० ॥
sarvābhedādanyatreme || 10 ||
sarvābhedāt—On account of non-difference everywhere; anyatra—in the other places; ime—these qualities (are to be inserted).
10. On account of the non-difference (of the Vidyā) everywhere (i.e. in all the texts of the different Śākhās where the Prāṇa Vidyā occurs) these qualities (mentioned in two of them are to be inserted) in the other places (e.g. the Kaushitaki Upanishad).
In the Chāṇḍogya and Brihadāraṇyaka Upanishads in the Prāṇa Vidyā we find the qualities of speech etc. as being richest and so on, are ultimately attributed to Prāṇa but not so in the Kaushitaki Upanishad, for instance.
The question is whether they are to be inserted in the Kaushitaki also, where they are not mentioned.
The Sutra says that they have to be inserted, since the Vidyā is the same in all the three Upanishads. Attributes of one and the same Vidyā have to be combined wherever that Vidyā occurs, although they may not be expressly mentioned.