They said, "Call upon your Lord to make clear to us what it is." [Moses] said, "[Allāh] says, 'It is a cow which is neither old nor virgin, but median between that,' so do what you are commanded."
They asked Moses to call on his Lord to clarify what the cow they had been told to sacrifice was like. Moses told them that Allah said that it was neither old nor young, but was between the two; and he told them to do what Allah had instructed them to.