Verse 2.9.2

तस्मिन्निमानि सर्वाणि भूतान्यन्वायत्तानीति विद्यात्तस्य यत्पुरोदयात्स हिंकारस्तदस्य पशवोऽन्वायत्तास्तस्मात्ते हिं कुर्वन्ति हिंकारभाजिनो ह्येतस्य साम्नः ॥ २.९.२ ॥

tasminnimāni sarvāṇi bhūtānyanvāyattānīti vidyāttasya yatpurodayātsa hiṃkārastadasya paśavo'nvāyattāstasmātte hiṃ kurvanti hiṃkārabhājino hyetasya sāmnaḥ || 2.9.2 ||

2. One should know that all beings that exist are dependent on the sun. The sun has a distinctive look before it rises, and that look is its hiṃkāra. The animals, who are dependent on the sun, also have their share in this hiṃkāra. That is why they make the sound hiṃ.

Word-for-word explanation:

Tasmin, on that [i.e., the sun]; imāni sarvāṇi bhūtāni, all these beings; anvāyattāni, are dependent; iti vidyāt, one should know this; tasya, of that [sun]; yat, the way [it looks then]; purodayāt, before it rises; saḥ, that [form]; hiṃkāraḥ, is hiṃkāra; paśavaḥ, the animals; tat asya anvāyattāḥ, are dependent on that [form] of it [i.e., of the sun as Sāma]; tasmāt, this is why; te, they; hiṃ kurvanti, make the sound hiṃ; hiṃkārabhājinaḥ hi etasya sāmnaḥ, they share in the hiṃkāra of the Sāma.

Commentary:

As the sun rises, it has a very pleasant and favourable look. This is called hiṃkāra. It is an expression of love and adoration for the Sāma. The animals are devoted to this hiṃkāra, for they also make the sound hiṃ as the sun rises. This is how they pay their tribute to the hiṃkāra of the Sāma.