They went out from us, but they didn't belong to us; for if they had belonged to us, they would have continued with us. But they left, that they might be revealed that none of them belong to us.

 (ii) In 1 John 2:29 John comes back to a thought which is never far from his mind. The only way in which a man can prove that he is abiding in Christ is by the righteousness of his life. The profession a man makes will always be proved or disproved by his practice. 