sanctuary - inviolable asylum, like the altar of the temple (1Ki 1:50; 1Ki 2:28; Eze 11:16; compare Pro 18:10); namely, to those who fear and trust in Him.
but ... offence - that is, a rock over which they should fall to their hurt; namely those who would not believe.
both ... houses - Israel and Judah. Here again the prophecy expands beyond the temporary application in Ahaz’ time. The very stone, Immanuel, which would have been a sanctuary on belief, becomes a fatal stumbling-block through unbelief. Jesus Christ refers to this in Mat 21:44. (Compare Deu 32:4, Deu 32:15, Deu 32:18, Deu 32:30, Deu 32:31, Deu 32:37; Dan 2:34; Rom 9:33; 1Pe 2:8).
gin - trap, in which birds are unexpectedly caught (Luk 21:35; 1Th 5:2). So at the destruction of Jerusalem under Titus.