Perhaps, the necessity for New Testament Canon and the urgency occurred because of the serious and severe departure from the Truth, resulting in spreading of false literature by Gnostics, whose prime leader, as some suppose is one named Marcion.
Marcion was an influential rich man, who owned a shipping company, which was the chief port of Pontus, at Sinope, in Turkey, on the southern shore of the Black Sea. He, who was a bishop, was also a great businessman.
Marcion’s theology refuted “Jehovah”, as seen in the Old Testament, on reasons that He was unapproachable, harsh, and unmerciful. By the end of 144 AD clergy of Christians in Rome discussed about his theology and saw that he was on purpose propagating monstrous doctrines that became huge threat to the Christendom. He was quickly excommunicated and his generous contributions made to the church were returned.
Scripture proves scripture and scriptures cannot be broken. Lord Jesus referred to Old Testament Scriptures several times and held Sadducees, Pharisees and Scribes held responsible and accountable for the knowledge in Scriptures.
If the Scriptures were not true how a Godly Jew would have considered the Book of Isaiah or Jeremiah or Chronicles as Scriptures. The Scriptures are God-breathed and not those that were written by a prophet purportedly revealed to him by God. If a palm is held against the mouth and man breathes out certain amount of pressure is felt; similar is the case of God-breathing out His words that became Scripture. God is not a creature but a Spirit, who cannot be seen by man’s physical eyes. He spoke to man in different ways in different dispensations. When he spoke to Prophets, they said “Thus says the Lord”, and when the Scripture from the Old Testament is quoted the phrase used is “it is written”. Anyone who despises John 1:1, and John 1:14 does not belong to God.
“In the beginning was the Word, and the Word was with God, and the Word was God” (John 1:1)
“And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth” (John 1:14)
The authority of the Scriptures was confirmed and ratified by Lord Jesus Christ.
“Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God” (1 John 4:2)
Lord Jesus did not leave behind any writing but His teachings were made available in writing by his disciples, the chief among who was Apostle Paul. His argument is noteworthy.
“Do we begin again to commend ourselves? or need we, as some others, epistles of commendation to you, or letters of commendation from you? Ye are our epistle written in our hearts, known and read of all men: Forasmuch as ye are manifestly declared to be the epistle of Christ ministered by us, written not with ink, but with the Spirit of the living God; not in tables of stone, but in fleshy tables of the heart” (2 Corinthians 3:1-3)
BUY BOOK HOW THE BIBLE CAME TO US
 “History of Dogma – Volume I” Ch.5:1, Christian Classics Ethereal Library n.d. web[04 June 2015]
 Example: Thus saith the LORD, Ye shall not go up, nor fight against your brethren the children of Israel: return every man to his house; for this thing is from me. They hearkened therefore to the word of the LORD, and returned to depart, according to the word of the LORD. (1 Kings 12:24); Also cf. 1 Chronicles 17:3–4; Jeremiah 35:13; Ezek. 2:4; Zech. 7:9; etc.
Notes: Cf. Jos 8:31; 2Sa 1:18; 1Ki 2:3; 2Ki 23:21; 2Ch 23:18; 25:4; 31:3; 35:12; Ezr. 3:2,4; 6:18; Ne 6:6; 8:15; 10:34,36; Es 1:19; 8:8-9; Ps 40:7; Isa 4:3; 65:6; Jer 17:1; 25:13; Da 9:13; Mt 2:5; 4:4,6-7,10; 11:10; 21:13; 26:24,31; Mr. 1:2; 7:6; 9:12-13; 11:17; 14:21,27; Lu 2:23; 3:4; 4:4,8,10; 7:27; 19:46; 24:46; Joh 6:31,45; 8:17; 10:34; 12:14; Ac 1:20; 7:42; 13:33; 15:15; 23:5; Ro 1:17; 2:24; 3:4,10; 4:17; 8:36; 9:13,33; 10:15; 11:8,26; 12:19; 14:11; 15:3,9,21; 1Co 1:19,31; 2:9; 3:19; 9:9-10; 10:7; 14:21; 15:45; 2Co 4:13; 8:15; 9:9; Ga 3:10,13; 4:22,27; Heb. 10:7; 1Pe 1:16; 1Jo 2:21
 cf. 1 Cor. 16:21; Gal. 6:11; Col. 4:18; 2 Thess. 3: 17; also Philemon 19