The hill of God is as the hill of Bashan; rather, a mountain of God is the mountain of Bashan. A sudden transition, and perhaps a quotation from an ancient poem. The special object of the psalmist's thought is not Bashan, but Mount Zion; and what he is about to celebrate is Jehovah's choice of Mount Zion for his dwelling place, and his establishment on it.
But he prefers to introduce the subject by a contrast with the great range of Canaan. Bashan, he says, is truly "a mountain of God"—i.e. a very great mountain (see the comment on Psalms 36:6)—"one which seemed in an especial degree to show forth creative power."
It is also an high hill; or rather, a mountain of peaks, containing numerous pointed summits. Yet God did not choose one of these for his habitation.