I have always believed that it is a wicked and adulterous generation that seeks after signs. So I have avoided that — sign seeking. But I learned something new. It all depends on the purpose for which you are seeking a sign. While listening to a commentary by Avraham Gileadi, I heard him explain the story about Ahaz as recorded in the book of Isaiah:

Ahaz was an unrighteous king of Judah and was facing further defeat when his enemies were invading his city. Isaiah tried to convince him that God would save Jerusalem — he told him to ask God for a sign  — but Ahaz did not trust God.

Again Jehovah addressed Ahaz, and said,

Ask a sign for yourself from Jehovah your God,

whether in the depths below or in the heights above. 

But Ahaz said, I will not. I will not put Jehovah to the test. (Isaiah 7:10-12)

Gileadi explains:

Isaiah’s word to Ahaz—“from Jehovah your God”—is twofold:

(1) it is a symbolic reminder of Jehovah’s covenant with King David, Ahaz’ ancestor, including the idea that the scheme to overthrow Ahaz will bring covenant curses on those who attempt it (vv 1-9); and

(2) it constitutes a “sign” or “confirmation” (’ot) that Jehovah will fulfill his promise (vv 10-17).

Ahaz, however, responds with pious hypocrisy, quoting Deuteronomy 6:16 about not putting Jehovah to the test. In his disloyalty and inability to believe Jehovah’s word, Ahaz refuses confirmation and thus puts himself above Isaiah. (IsaiahExplained.com)

Instead, Ahaz sends treasures from the temple to Tiglath-Pileser, the king of Assyria. He makes his alliance with Tiglath instead of God — “I am your servant and son. Save me from the hands of the kings of Syria and Israel who have gone to war against me.”

Then Isaiah said, Take heed, O house of David! Is it not enough for you to try the patience of men? Must you also try the patience of my God? (Isaiah 7:13)

When and why is it ok to ask God for a sign?

If King Ahaz had been loyal to the Lord, he would have believed Isaiah. But Ahaz is not a loyal vassal. He does not believe. Isaiah tells Ahaz to ask God for a sign as a confirmation [the word sign or miracle is the same word in Hebrew]. It is ok to ask for a sign as a confirmation, just as Gideon asked God.  — That’s different than asking for some miraculous thing to consume it upon your lusts.  After all, signs follow those who believe.

In the Bible, Gideon asks God for a sign that He will deliver Israel:

Then Gideon said to God, “If You will deliver Israel through me, as You have spoken, behold, I will put a fleece of wool on the threshing floor. If there is dew on the fleece only, and it is dry on all the ground, then I will know that You will deliver Israel through me, as You have spoken.”

And it was so. When he arose early the next morning and squeezed the fleece, he drained the dew from the fleece, a bowl full of water.…(Judges 6: 36-38)

Gideon is still not sure (ahh our human condition) and he asks God one more time for a sign, to confirm what he believes to be true, so that he could go confidently to battle:

Then Gideon said to God, “Do not let Your anger burn against me that I may speak once more; please let me make a test once more with the fleece, let it now be dry only on the fleece, and let there be dew on all the ground.”…

God did so that night; for it was dry only on the fleece, and dew was on all the ground. (Judges 6: 39-40)

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Gideon and the fleece

Gideon and the feece