Therefore the Lord himself shall give you a sign; Behold, a virgin shall conceive, and bear a son, and shall call his name Immanuel.
Isaiah gave this prophecy not as a word of encouragement but as a rebuke of unbelief. The context provided by the chapter is that the Assyrians are invading Israel and trying to take Jerusalem. The king and the people are afraid and God promises King Ahaz that they will not succeed.
10 Moreover the Lord spake again unto Ahaz, saying,
11 Ask thee a sign of the Lord thy God; ask it either in the depth, or in the height above.
12 But Ahaz said, I will not ask, neither will I tempt the Lord.
Ahaz was trying to be clever and use God’s own word against much in the same way that Satan tried to twist scripture against Jesus during His temptation. I believe Ahaz knew better that asking for a sign as a condition of faith was prohibited but here the Lord was offering it to him and so it was okay. In spite of what Ahaz said he, in fact, was testing God’s patience.
Jumping forward to the ministry of Jesus we read that He was frustrated with the people because they wanted Him to perform miracles, saying,”Except ye see signs and wonders, ye will not believe” (John 4:48). This was the proper application of the command that Ahaz was using as cover for not trusting God.
God requires us to trust and obey before we see a miracle. We want to see signs and wonders before we trust Him, maybe. Jesus said that the centurion had faith like no one in Israel because he did not need to see the healing to believe it.
We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts.
2 Peter 1:19
Peter saw the miracles of Jesus’ ministry and I don’t think they can be matched by anyone in the Bible or human history. Yet, it was the word that was a more solid foundation for faith. Miracles, signs, emotional experience, all of these will fail us. You have to decide at the outset that God is trustworthy and commit yourself.