First, John outline to anyone reading, unbelievers particularly, that God came in the flesh, that John and his fellow disciples saw him, touched Him, heard Him. Then, John declares to "my dear children", those who believe in Jesus, that He is (not was or will be) our propitiation. He also explains what growth in Christ is all about: seeing more of Jesus, Him who has been from the beginning (1 John 2:14-15).
At the beginning of the third chapter, John has to grab our attention. We are not just believers, we are not just dear children of elders in the Body of Christ. . .
We are sons of God! We are His children, and He is our Father!
Have you taken time to behold this wonderful revelation?
Paul invited his fellow Corinthians to behold Jesus:
"Now the Lord is that Spirit: and where the Spirit of the Lord is, there is liberty. 18But we all, with open face beholding as in a glass the glory of the Lord, are changed into the same image from glory to glory, even as by the Spirit of the Lord." (2 Corinthians 3: 17-18)
John explains specifically what happens to us when we see ourselves more and more in Christ, as sons of the living God:
"Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. 3And every man that hath this hope in him purifieth himself, even as he is pure." (1 John 3: 2-3)
It's time for us to behold who we are in Christ, sons of the Living God, no longer orphans or alienated from our Loving Father:
"For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father." (Romans 8: 15)
and of course:
"Herein is our love made perfect, that we may have boldness in the day of judgment: because as he is, so are we in this world." (1 John 4: 17)