What we see and hear matters

A man is defiled by what come out of him, not by what goes into him. Jesus is concerned about our hearts. He makes this point throughout the Gospels. The Beatitudes are an example where he equates anger to murder and lust to adultery. Whether or not you actually physically commit murder or adultery, is not any more important to God than if you desire these sins in your heart.

My hardened heart

The twelve apostles had just returned from an awesome mission trip. They had seen the power that God had given them at work so that God cast out demons and healed diseases through them. Jesus wanted them to get away, perhaps so they could decompress and reflect on the power of God that they had experienced firsthand. Unfortunately, their retreat was caught short as the crowds followed them on foot and met them when they got to shore. This sets up another miracle for Jesus as he feeds the 5000 men (plus however many women and children) with just five loaves and two fish. After this, the disciples see Jesus walk on water, and calm the wind.