The Religion and Philosophy of the Veda and Upanishads v1.c19.s1.2

v1.c19.s1.2

It appears that there are strictly three Ṛbhus, named Ṛbhukṣan, 'lord' or 'chief of the Ṛbhus', which is also an epithet of Indra, Vāja, and Vibhvan. It was, however, natural that the number should be increased, and we hear of all the Ṛbhus, or Ṛbhu with the Ṛbhus, or Vibhvan with the Vibhus, and, it may be added, the Praiṣa for the god Indra at the evening pressing in one version adds Prabhus. They are called Saudhanvanas, offspring of Sudhanvan, 'the good archer', or sons of Indra, and by a play on Indra's epithet, 'son of strength', they appear as 'descendants of strength'. On the other hand they are also sons of Manu, and claim Agni as brother. They are bright deities, who ride on a car drawn by fat steeds; they have metal helmets and fair necklaces.