Isaiah 7:11

“Ask thee a sign of the Lord thy God, &c.] For though Ahaz was a wicked man, yet the Lord was his God, as he was the God of the people of Israel in general, as a nation; and knowing his unbelief and diffidence of his word unto him, offers to confirm it by a sign or miracle: ask it either in the depth, or in the height above, in earth, or in heaven: so the Targum, “ask that a miracle may be done for thee upon earth, or that a sign may be shown thee in heaven;” either that the earth might gape and open its mouth, as in the days of Moses; or that the sun might stand still, as in the times of Joshua; or that a dead man might be raised out of the depth of the earth; or that there might be some…”

“Ask thee--since thou dost not credit the prophet's words. sign--a miraculous token to assure thee that God will fulfil His promise of saving Jerusalem (Isa 37:30; Isa 38:7-8). "Signs," facts then present or near at hand as pledges for the more distant future, are frequent in Isaiah. ask . . . in . . . depth--literally, "Make deep . . . ask it," that is, Go to the depth of the earth or of Hades [Vulgate and LOWTH], or, Mount high for it (literally, "Make high"). So in Mat 16:1. Signs in heaven are contrasted with the signs on earth and below it (raising the dead) which Jesus Christ had wrought (compare Rom 10:6-7). He offers Ahaz the widest limits within which to make his choice.”

“Ask thee - Ask for “thyself;” ask a sign that shall be convincing to “thyself,” since thou dost not fully credit the words of the prophet. It is evident that the words of the prophet had made no impression on the mind of Ahaz. God, therefore, proposes to him to ask any “proof or demonstration” which he might select; anything that would be an indication of divine power that should put what the prophet had said beyond doubt. Had Ahaz put confidence in God, he would have believed what the prophet said without miraculous proof. But he had no such confidence. ‘The prophet, therefore, proposes that he should ask any miraculous demonstration that what he said would come to pass. This proposition…”

“7:11 A sign of confirmation would be performed before Ahaz’s eyes as a token of God’s truthfulness. His son Hezekiah would also receive such a sign (see 37:30).”

“a sign: Isa 37:30, Isa 38:7, Isa 38:8, Isa 38:22; Jdg 6:36-40; Kg2 20:8-11; Jer 19:1, Jer 19:10, Jer 51:63, Jer 51:64; Mat 12:38-40, Mat 16:1-4 ask it either in the depth: or, make thy petition deep Isaiah 7:12”