Everyone who has this hope set on him purifies himself, even as he is pure.
Purifies himself --  CP: "Purity does not come to the Christian through anything the Christian is or has done. Purity comes about through the shedding of Jesus’ blood on the cross. -- Nothing but the blood of Christ can remove the guilt and stain of sin on our lives (see 1 John 1:7; 1 Peter 1:22; 2 Corinthians 7:1)." Note especially 1 Peter 1:22, One purifies himself by his obedience to the truth, in which the blood of Christ washes away his sins (Acts 22:16 Revelation 1:5.).