God is instructing you to leave the shallow waters and go into deep waters. Spiritually where you are at is not enough, he wants you to go deeper. Are you in the shallow or in the deep? Paul is telling us to move beyond elementary teachings about christ. The elementary teaching is that Jesus is the only son of God, who came to take away the sins of the world,  Jesus is the way, the truth and the life. Jesus is the resurrection and the life, those who believe in him will never die but have everlasting life. We have to go beyond this elementary teaching about Christ to a deeper understanding.