Mark 8 begins with Jesus feeding the 4000 with a few loaves and fish. He did a similar thing with a crowd of 5000 back in Mark 6. Soon after feeding the crowd he gets in a boat with His disciples and heads across the lake. They land and are immediately met with a group of religious leaders demanding a sign. It’s important that we pause here and reflect. For anyone serious about seeing If Jesus were the messiah or not, there were already plenty of signs. Jesus had fulfilled prophecy, healed people, fed massive crowds on a few loaves and some fish, and even taught in the synagogues. But still these leaders were looking for a sign. A sign not to believe him, not to follow him, but a sign to test him.
Jesus responds that their won’t be a sign and hops back in the boat with the disciples and they head off on the lake again. While in transit Jesus mutters, “beware the leaven of the Pharisees” (religious leaders). The disciples think it’s a backhanded rebuke for forgetting to bring the bread. Jesus reminds the that he fed the 5000 and 4000 with just a few loaves of bread and fish. He doesn’t want bread, he wants them to be aware that the kind of doubt that is constantly looking for a sign (though plenty are evident) is both dangerous and contagious.
The point: When you already know the will of God follow it with obedience, don’t keep testing. If God has called you to ministry, go. If You know Gods will but refuse to follow for the sake of testing, isn’t that disobedience? I’ve heard other pastors tell stories of how they put the fleece out before God wanting Him to confirm something in their life (the fleece story comes from judges 6:36-40 where Gideon, knowing the will of the Lord (v36), puts out a fleece to confirm what he already knows). I can understand this if they are uncertain about an issue and want to know that God is in it or if they doubt their own heart and wonder if their motives might be mixed and need clarity. But to know the will of God, or in the case of Jesus, to know by signs, wonders, and prophecy that Jesus is the Messiah and to still demand a sign is flat out disobedience.
This kind of disobedience is contagious and dangerous. Whole congregations can be lead astray by doubting the will of God and refusing to follow on faith in His promises.