You know that he was revealed to take away our sins, and in him is no sin.

 (ii) That may well be so but there is more to it. In the Greek there is a subtle difference in tenses which makes a very wide difference in meaning. In 1 John 2:1 it is John's injunction that you may not sin. In that verse sin is in the aorist tense which indicates a particular and definite act. So what John is saying is quite clearly that Christians must not commit individual acts of sin; but if they do lapse into sin, they have in Christ an advocate to plead their cause and a sacrifice to atone. On the other hand, in our present passage in both cases sin is in the present tense and indicates habitual action. 