That which was from the beginning, that which we have heard, that which we have seen with our eyes, that which we saw, and our hands touched, concerning the Word of life
The second reason why he wrote this epistle is in chapter 2, verse 1 John 1:1 . "These things write we unto you, that ye sin not." And so, the purpose of this epistle is to bring to you a life of victory over sin, to give you power over sin.