The third Mandala of the Rigveda has 62 hymns, mainly to Agni and Indra. 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).[1] Most hymns in this book are attributed to viśvāmitra gāthinaḥ
The verse 3.62.10 gained great importance in Hinduism as the Gayatri Mantra.