As the oldest living apostle and chief leader among the churches, John had the right to address the believers as his "little children." He is writing to ensure they don't fall into sin by disbelieving in Christ. The intention of the antichrist is to get them to doubt that Jesus was the Christ - to move them to unbelief! John assures them that this sin of unbelief can be conquered through the power of the Holy Spirit.
Jesus not only paid the price for the sins of the those who believe, but for the sins of the whole world. We have an advocate as a friend, a Comforter who has access to the Father, who by the Spirit, abides with us, showing that we have not lost ground but are His - and this Comforter confirms this to us.
1 John 1:6-10
John's words point to the vivid recollection of the person of Jesus that John still had in his old age. For John those memories were permanently etched on his mind as if the events had just happened. He uses terms such as "we have heard" "we have seen" "we have looked upon" and "our hands have handled" that strongly affirm the physical reality of the incarnation of Jesus.
John's personal testimony refutes the false teachers who boasted arrogantly and wrongly about the Christ they had never seen or known. John wanted his readers to be partakers with him in possessing eternal life. We can have fellowship with the Father and with His Son Jesus Christ, which ultimately produces a fullness of joy.
2 Peter 3:14-18 Final Words
14 Therefore, beloved, since you are waiting for these, be diligent to be found by him without spot or blemish, and at peace. 15 And count the patience of our Lord as salvation, just as our beloved brother Paul also wrote to you according to the wisdom given him, 16 as he does in all his letters when he speaks in them of these matters. There are some things in them that are hard to understand, which the ignorant and unstable twist to their own destruction, as they do the other Scriptures. 17 You therefore, beloved, knowing this beforehand, take care that you are not carried away with the error of lawless people and lose your own stability. 18 But grow in the grace and knowledge of our Lord and Savior Jesus Christ. To him be the glory both now and to the day of eternity. Amen.
John sums up all he had learned from Jesus in the message: " ... that God is LIGHT, and in Him is no darkness AT ALL." Light in the Scriptures is the emblem of perfect purity, truth, knowledge, prosperity, and joy. In Him, there is NO darkness at all, not even a pin-prick. Where there is pure light, there is pure love. On the other hand, darkness is the absence of light. When people stray from believing in God and having love for others, they step back into the darkness and act in ways that are inconsistent with His character. Darkness represents what is sinful and evil. God is untainted by any evil or sin. Because "God is light" He alone can guide people out of the darkness of sin and unbelief.
2 Peter 3:8-10
8 But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day. 9 The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance. 10 But the day of the Lord will come like a thief, and then the heavens will pass away with a roar, and the heavenly bodies will be burned up and dissolved, and the earth and the works that are done on it will be exposed.
Introduction to 1st John
2 Peter 3:5-7
5 For they deliberately overlook this fact, that the heavens existed long ago, and the earth was formed out of water and through water by the word of God, 6 and that by means of these the world that then existed was deluged with water and perished. 7 But by the same word the heavens and earth that now exist are stored up for fire, being kept until the day of judgment and destruction of the ungodly.