Now when Jesus heard this, he withdrew from there in a boat to a deserted place by himself.  But when the crowds heard it, they followed him on foot from the towns.  When he went ashore, he saw a great crowd; and he had compassion for them and cured their sick.  When it was evening, the disciples came to him and said, "This is a deserted place, and the hour is now late; send the crowds away so that they may go into the villages and buy food for themselves."  Jesus said to them, "They need not go away; you give them something to eat."  They replied, "We have nothing here but five loaves and two fish."  And he said, "Bring them here to me."  Then he ordered the crowds to sit down on the grass.  Taking the five loaves and the two fish, he looked up to heaven, and blessed and broke the loaves, and gave them to the disciples, and the disciples gave them to the crowds.  And all ate and were filled; and they took up what was left over of the broken pieces, twelve baskets full.  And those who ate were about five thousand men, besides women and children.

Jesus had been teaching the crowd (throughout chapter 13) what the kingdom is like through the use of parables: a treasure, a pearl, leaven.  Now he teaches them through the miraculous event of the multiplication of the loaves.  First their sick were cured then their physical hunger was completely satisfied.  The evangelist Matthew takes care to record precisely "all ate and were filled."  No one was overlooked, Jesus made plenty for all.  "Whoever comes to me will never be hungry." (John 6.35)  The physical is a sign of the spiritual.

After everyone ate and everyone was filled the leftovers are carefully gathered so that nothing is wasted.  All of God's gifts are precious and to be handled wisely; we are never to be wasteful.  In John's account of this miracle Jesus says explicitly: "Gather up the fragments left over, so that nothing may be lost." (John 6.12)  But why was so much left over?  Surely Jesus could have made just enough.  As with the hundreds of gallons of wine at Cana, because this miracle is a deeper sign of the generosity and abundance of God Jesus wants to show just how overflowing the kingdom is.  There is not simply fullness for all but overflowing abundance everywhere.  "Give, and it will be given to you.  A good measure, pressed down, shaken together, running over, will be put into your lap." (Luke 6.38)