John 3:16 is cited so often because it is the most succinct way of putting the Gospel. John 3:16 (KJV) For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. The longer version is that you are a sinner who has trangressed against God and deserve death because of it. Romans 3:10-12 (KJV) As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. Romans 6:23 (KJV) For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. 1 John 1:8, 10 (KJV) If we say that we have no sin, we deceive ourselves, and the truth is not in us. [...] If we say that we have not sinned, we make him a liar, and his word is not in us. As a mere human, you are incapable of atoning for your sin through personal effort or through the efforts of another mere human. Isaiah 64:6 (KJV) But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away. Ephesians 2:8-9 (KJV) For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. Hebrews 10:11 (KJV) And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins: For this reason God sent His only begotten Son to earth to die for the sins of the world because while no mere man with his flaws and sin can save himself or others a perfect man who is God in the flesh can offer an sacrifice (Himself) which more than covers the sins of the world. John 6:39-40 (KJV) And this is the Father's will which hath sent me, that of all which he hath given me I should lose nothing, but should raise it up again at the last day. And this is the will of him that sent me, that every one which seeth the Son, and believeth on him, may have everlasting life: and I will raise him up at the last day. 2 Peter 3:9 (KJV) The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. Hebrews 10:10, 12 (KJV) By the which will we are sanctified through the offering of the body of Jesus Christ once for all. [...] But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God; 1 John 2:1-2 (KJV) My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: And he is the propitiation for our sins: and not for our's only, but also for the sins of the whole world. He died and was buried. Then He rose miraculously fulfilling prophecy, proving His sacrifice was successful and He was victorious over sin and death. Luke 24:19-26 (KJV) And he said unto them, What things? And they said unto him, Concerning Jesus of Nazareth, which was a prophet mighty in deed and word before God and all the people: And how the chief priests and our rulers delivered him to be condemned to death, and have crucified him. But we trusted that it had been he which should have redeemed Israel: and beside all this, to day is the third day since these things were done. Yea, and certain women also of our company made us astonished, which were early at the sepulchre; And when they found not his body, they came, saying, that they had also seen a vision of angels, which said that he was alive. And certain of them which were with us went to the sepulchre, and found it even so as the women had said: but him they saw not. Then he said unto them, O fools, and slow of heart to believe all that the prophets have spoken: Ought not Christ to have suffered these things, and to enter into his glory? If you but believe on Jesus as the sacrifice your sin, you are washed of your sin, made righteous and saved permanently. Acts 22:14-16 (KJV) And he said, The God of our fathers hath chosen thee, that thou shouldest know his will, and see that Just One, and shouldest hear the voice of his mouth. For thou shalt be his witness unto all men of what thou hast seen and heard. And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord. Romans 4:20-25 (KJV) He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God; And being fully persuaded that, what he had promised, he was able also to perform. And therefore it was imputed to him for righteousness. Now it was not written for his sake alone, that it was imputed to him; But for us also, to whom it shall be imputed, if we believe on him that raised up Jesus our Lord from the dead; Who was delivered for our offences, and was raised again for our justification. Ephesians 1:12-14 (KJV) That we should be to the praise of his glory, who first trusted in Christ. In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise, Which is the earnest of our inheritance until the redemption of the purchased possession, unto the praise of his glory. Acts 16:31 (KJV) And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house. Romans 10:9-10 (KJV) That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. More on reddit.com

If I, a teenager who use to sin just got saved, so can you.

Praise God! Welcome home!

There’s an on going war between spirit and flesh but trusting in the gospel will allow your spirit side to fight against the flesh and get you on the right path with God.

I want to encourage you with some even better truth. It's true that by trusting in the Gospel you receive new life, and in that spiritual life you fight against your sins, but the way you've said that makes is sound like that by fighting this fight that you get on the right path with God. The good news of the gospel is that you are put on the right path with God by grace, not because of anything you do. Christ, by his holy life and perfect obedience, fulfilled all righteousness, which is now yours: "For our sake he made him to be sin who knew no sin, so that in him we might become the righteousness of God." 2 Cor. 5:21. So, it is actually out of our already being forgiven and given righteousness at Christ, and the perfect standing we have with God because of that, that we then fight against sin.

Rest in it, brother!

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The short answer is because he didn't really write the Gospel of John (and the author never even claims to be John). The longer answer is a different theological agenda. If the community that produced GJohn knew about the transfiguration story (and they may have. They seem to have at least some knowledge of Synoptic traditions), my guess is that it was omitted because they thought it seemed to lower the Christology. For the Gospel of John, Jesus was eternally preexistent and already glorified, so he couldn't have been further transfigured. Plus, they might not have liked the idea of Jesus being equated to two Jewish prophets. It might have seemed like a downgrading. GJohn is always concerned with making Jesus more divine that the Synoptics. The glossing of John's baptism for example or the altering of Jesus' demeanor on the cross from distressed to pacific. More on reddit.com

Hello! ☺️ 1 Corinthians 15. 15 Moreover, brethren, I declare to you the gospel which I preached to you, which also you received and in which you stand, 2 by which also you are saved, if you hold fast that word which I preached to you—unless you believed in vain.3 For I delivered to you first of all that which I also received: that Christ died for our sins according to the Scriptures, 4 and that He was buried, and that He rose again the third day according to the Scriptures. More on reddit.com