Luke 11 v 29. “As the crowds increased, Jesus said, “This is a wicked generation. It asks for a miraculous sign, but none will be given it except the sign of Jonah”.
Why did Christ turn down the request for a sign as recorded in v 16? Because He had already done many miracles which many of his questioners would have either seen or heard about. In addition to his already public track record, He had just healed a man afflicted with dumbness because of an evil spirit, and He had done it before them all.
The moral quality of His deeds, and the origins of His power was self-evident and it was always consistent. To suggest then, as these people were doing, that there was a reasonable possibility that what Jesus did was display a supernatural power with its roots from the devil, and therefore they needed another sign to convince them, was monstrous and perverse. If the miracles Christ had already done did not prove to them who he was and where he came from, then what kind of miracle would ever prove it?
The truth is that the people who had demanded another sign would not have believed in him, no matter what sign He did.
They had already made up their minds about him. Their seeking for a sign was not an indication of their willingness to believe in him, but rather they were rationalising their inbuilt and stubborn unwillingness to believe in Him and follow him.
If he had tried to give them another sign, he would have been tacitly admitting that their doubts about him were reasonable.
Christ is never deceived by their requests.
Do you recognise this spirit in the discussions you have with your friends? It is not that they need evidence or arguments to persuade them. Their minds are already made up and no argument will sway them. That refusal to believe in the face of all rational and reasonable discussion is a wickedness that belongs to the same realm as the wickedness with which Jesus charged his contemporaries.