Rigveda 8.001.10

Now I pour the full-milked oblation to Gayatri: Indra, the cow, drawn from abundant milch-cows, with flesh and strength fashioned, accept it.

I invoke today the all-sufficient Indra, as the milch cow yielding abundant milk, of excellent motion, andeasy to be milked; or, as another (form), the vast-dropping, desirable (rain).

This day I call Sabardugiha who animates the holy song, Indra the richly-yielding Milch-cow who provides unfailing food in ample stream.