God has never asked anyone to believe anything that does not rest upon a foundation. Faith does not mean to move blindly into some area and say, "Oh, I am trusting God." That is very foolish. God never asks us to do that. For example, in our salvation we do not bring a little lamb to offer as a sacrifice; our faith rests upon the historical facts of the death, the burial and the resurrection of the Son of God. God never asks us to take a leap in the dark. He asks us to believe and trust something which rests upon a firm foundation, and it is the only foundation, "For other foundation can no man lay than that is laid, which is Jesus Christ" (1 Corinthians 3:11). If any person is an honest unbeliever and sincerely wants to know God, he will come to a saving faith. Folk with whom I have dealt who say that they cannot believe are not being honest. The fact of the matter is that no man's eyes are blindfolded unless he himself chooses to be blindfolded. If a person really wants to know God and will give up his sin and turn to Christ, God will make Himself real to him. In our day the problem is that a great many folk do not really mean business with God.
That was the problem with King Ahaz — he didn't mean business with God. God knew that Ahaz didn't have faith, and He was willing to give the king faith; but Ahaz was nothing but a pious fraud — and there are a lot of those around today. Listen to his false piety: "But Ahaz said, I will not ask, neither will I tempt the LORD" (Isaiah 7:12). Isn't that sweet of him? He sounds so nice, but he is one of the biggest hypocrites you will find in Scripture. This sort of thing is sickening, and I believe God feels that way about it.
And he said, Hear ye now, O house of David; Is it a small thing for you to weary men, but will ye weary my God also? (Isaiah 7:13)
My friend, don't think you are being pious when you say, "Oh, I won't test God." God says, "Test Me. Try Me, and see if I am not good." I actually feel fatigued when I talk to some folk who say that they are just going to step out on "faith." Oh, my friend, wait until God puts a rock underneath you. Wait until God gives you definite leading before you make a fool of yourself and bring criticism upon the cause of Christ.
God said to this unbelieving king, "I'm not asking you to believe My message just because Isaiah said it. I want to put a foundation under it. I want to give you a supernatural sign so you will know that the message is from Me." But Ahaz refused to ask for a sign. So God gave a sign — not to Ahaz - but to the whole house of David.
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 7:14)
—From Edited Messages on Isaiah by Dr. J. Vernon McGee