His knowledge: This does not mean knowledge in the sense of ideas in the mind. It refers to everything the servant would live through. It includes his obedience, his suffering, and his close relationship with God.
Because the servant obeys God fully, many people can be put right with God. This is called justification (God declaring a person to be right with him). He can do this because he will carry and bear their sins (see Genesis 15:6; Romans 5:18–19).