Mark 8:11-15

Mark 8:11 (KJB)
And the Pharisees came forth, and began to question with him, seeking of him a sign from heaven, tempting him.

The Pharisees were the strict legalistic separatists who demanded total obedience to a great amount of tradition which was passed down through the ages. The Sadducees rejected the traditions of the Pharisees and also rejected the idea of resurrection, angels, and devils plus they only accepted the five books of Moses as authoritative. They had already seen the miracles of Jesus which were definitely signs pointing to the deity of Jesus. However, this was not good enough for these groups. They wanted a specific sign to be given to them, probably one that they would concoct themselves which would cause Jesus to sin by breaking some law. They wanted to put Him to the test to see if He really was who He claimed to be. How unwise they were because how could anyone do the miracles Jesus did unless it was God doing them? They came to Jesus in the region of Dalmanutha which was on the northwest shore of the sea of Galilee in the vicinity of Magdala.

Mark 8:12 (KJB)
And he sighed deeply in his spirit, and saith, Why doth this generation seek after a sign? verily I say unto you, There shall no sign be given unto this generation.

(Mat 12:39 KJV) But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas: The essence of living the Christian life is to live it by faith and the opposite of that is to live by sight. (2 Cor 5:7 KJV) (For we walk by faith, not by sight:) It is not that a sign is something sinful as in the past God had done this, Gideonís fleece, Ahaz in Isaiah 7, or Hezekiah in 2 Kings 20. Jesus here was speaking directly to the unrepentant Jews of that day who disbelieved the ministry of Christ and opposed Him. They did not even recognize any of the signs and miracles that He had done previously because they had walked away from God and created their own system of beliefs via their writings. Jesus was not willing to give them a sign at that particular time but they will get the sign they are looking for by means of looking at the prophet Jonah as found in Matthew 12:39. They would have been familiar with the prophet Jonah but they would have to study it to see what the sign might be so they could recognize it when it happens. They would have to make a comparison between Jonah and Christ being resurrected. The way they were so spiritually dull, it would have been a miracle in itself if they made the association.

Mark 8:13 (KJB)
And he left them, and entering into the ship again departed to the other side.

Once Jesus had given them the key of the sign they had looked for, He had entered into a ship and had departed to the other side of the Sea of Galilee. They were heading to Bethsaida Julias at this time which was on the northeast corner of the Sea.

Mark 8:14 (KJB)
Now the disciples had forgotten to take bread, neither had they in the ship with them more than one loaf.

Now the disciples had crossed from the western shore of Galilee to the eastern shore where there were mixed races and they would not be able to find a Jewish bakery to buy bread. They had probably thought they had a lot of bread left over from the seven large baskets but it looked like they forgot to check their supplies before they left land. This may have also happened because the departure of the Lord Jesus Christ from the Pharisees and Sadducees was quite hasty. One loaf would definitely not feed all of them.

Mark 8:15 (KJB)
And he charged them, saying, Take heed, beware of the leaven of the Pharisees, and of the leaven of Herod.

Then Jesus turns the situation into a teaching for the benefit of the disciples concerning the Sadducees and Pharisees. The disciples would have understood that leaven was a picture of evil which had the ability to completely permeate whatever it attacked. A person could tempt himself with a little leaven of sin and pretty soon they are permeated with that sin. We could see that principle in drug use, cigarettes, alcohol, sex, etc., anything which causes an unhealthy addiction. Here is the only addiction the Christian should have. (1 Cor 16:15 KJV) I beseech you, brethren, (ye know the house of Stephanas, that it is the firstfruits of Achaia, and that they have addicted themselves to the ministry of the saints,) What Jesus was warning the disciples against here was that they should not adopt the leaven of the Pharisees and Sadducees/Herod. It had nothing to do with physical bread but their teachings and their lifestyles. They had misled the people of Israel in their teachings and Jesus wanted to make sure they had checked themselves regularly to make sure they were not drifting in that direction since pretty soon they would become teachers of the Gospel. The leaven of Herod was also the leaven of the Sadducees since the Herodians were a part of the sect of the Sadducees. (Mat 16:6 KJV) Then Jesus said unto them, Take heed and beware of the leaven of the Pharisees and of the Sadducees. The leaven of Herod could also be associated with secularism.