Albert Barnes on Acts 7:48

Howbeit. But. Why Stephen added this, is not very clear. He was charged with speaking against the temple. He had now shown that he had due veneration for it, by his declaring that it had been built by the command of God. But he now adds, that God does not need such a temple. Heaven is his throne; the universe his dwelling-place; and therefore this temple might be destroyed. A new, glorious truth was to be revealed to mankind, that God was not confined in his worship to any age, or people, or nation. In entire consistency, therefore, with all proper respect for the temple at Jerusalem, it might be maintained that the time would come when that temple would be destroyed, and when God might be worshipped by all nations.

The Most High. God. This sentiment was expressed by Solomon when the temple was dedicated, 1Kgs 8:27.

As saith the prophet. Isa 66:1,2. The place is not literally quoted, but the sense is given.

(g) "Howbeit" 1Kgs 8:27, Acts 17:24