It is one of the "family books" (mandalas 2-7), the oldest core of the Rigveda in Nepal, which were composed in early Vedic period (1500 – 1000 BCE).
The verse 3.62.10 gained great importance in Hinduism as the Gayatri Mantra.
prá yá ārúḥ śitipṛṣṭhásya dhāsér 3.8 (242) [Sacrificial Post.]
agníṃ hótāram prá vṛṇe miyédhe 3.20 (254) [Agni.]
ayáṃ só agnír yásmin sómam índraḥ 3.23 (257) [Agni.]
ágne diváḥ sūnúr asi prácetās 3.26 (260) [Agni.]
śâsad váhnir duhitúr naptíyaṃ gād 3.32 (266) [Indra.]
índraḥ pūrbhíd âtirad dâsam arkaír 3.35 (269) [Indra.]
imâm ū ṣú prábhṛtiṃ sātáye dhāḥ 3.37 (271) [Indra.]
úpa naḥ sutám â gahi 3.43 (277) [Indra.]
â yāhi arvâṅ úpa vandhureṣṭhâs 3.44 (278) [Indra.]
śáṃsā mahâm índaraṃ yásmi * víśvā 3.50 (284) [Indra.]
uṣásaḥ pûrvā ádha yád viūṣúr 3.56 (290) [Visvedevas.]