Just after Jesus feeds 4,000 people with seven loaves and a few fish earlier in Mark 8, the Pharisees came and began to argue with Him. They requested a sign from heaven in order to test Him.
The Pharisees followed Jesus almost everywhere and certainly they had seen signs and miracles. They were much like the Israelites in the wilderness. The Lord has made Himself known to every nation by His might, yet the people of God still have doubts. Their hardness of heart leads to their unbelief.
The Pharisees are so settled in their unbelief as if nothing can unsettle them – even the signs and wonders.
The disciples and Jesus got into the boat and returned to the lake, after their conversation with the Pharisees. The disciples had forgotten to bring bread. So, Jesus took this opportunity to caution His disciples about the “leaven of the Pharisees”. However, the disciples were clearly missing out what Jesus was trying to say. They began discussing with one another the fact that they had no bread. Even the clear reference to the leaven of the Pharisees and Herod were completely ignored.
The disciples had seen Jesus walking on water, healing the sick, raising the dead, driving out unclean spirits, casting out demons, calming a storm, and now multiplying bread. Yet, their hearts were still hardened.
How many more miracles do you want to see?
The problem is not the evidence.
The problem is in them/us.
Do you not yet perceive or understand? Are your hearts hardened? (Mark 8:17)
Would you once and for all make up your mind, and choose to put your trust in Jesus and dedicate your life to Him?