Mandala 3, credited to the Vishvamitra family, holds a single verse, 3.62.10, whose later fame vastly outstrips its modest place within a 62-hymn book: the Gayatri Mantra, addressed to Savitr, the sun as a divine impeller of all activity, praying "may we attain that excellent glory of Savitr the god, that he may stimulate our thoughts."
Recited daily by observant Hindus for millennia as part of the morning sandhya ritual, and central to the sacred thread ceremony marking a young brahmin's formal initiation into Vedic study, the Gayatri Mantra is widely regarded as the single most recited verse in the entire Hindu tradition, its fame reaching so far beyond its Rig Vedic origin that many who chant it daily may not know its exact mandala or hymn number. Vishvamitra himself is one of Hindu tradition's most vividly storied rishis, a warrior-king in later legend who through fierce asceticism earned the rank of brahmin sage, a dramatic caste transformation narrated at length in the later epic and Puranic literature far beyond anything the Rig Veda itself narrates about him. The rest of the mandala follows the standard family-book pattern, hymns to Agni and Indra dominating, composed in the same ritual, request-driven register as the other family books surrounding it.