Mark 7:1-23 Mark records this account of the Pharisees questioning Jesus about the disciples failing to wash their hands. This refers to ceremonial washing. The Pharisees are committed to their traditions, but are actually hiding their own sinful hearts behind their traditions. This is possible for us today as well. We can hide behind our church involvement, but miss the point of his coming to earth - transformation of the heart. Defilement does not come from what you eat, according to Jesus, it comes from within - it comes from our impure hearts, desires and longings. Tradition can mask the sinfulness of our hearts, we must instead focus on actions and attitudes that come out of us.
The gospel of Mark focuses on the gospel of Jesus, who is the Son of God. Jesus is the Christ, the promised one from God. Mark refers to Jesus as the Son of Man, emphasizing his humanity and the Son of God which emphasizes his deity. The influence of Peter or the teaching of Peter is the foundation of the gospel of Mark. Mark writes to explain Jesus to unbelievers and to call believers to know him and live like him. Mark emphasizes Jesus as a servant, a quality believers should emulate. Mark also emphasizes the discipleship of Jesus. Jesus discipled his followers. Mark hopes to demonstrate the good news (gospel) of Jesus to the world, because he is the Son of God.