We find that in the New Testament, teachings of Jesus Christ are recorded in four Gospels by four different apostles.
Why did God give us four Gospels instead of just one?
The preliminary suggestion to make the four gospels part of the canon, came from a catholic Bishop Iranaeus of Lyons (France today) in c. 180. He said there should be four because there are four beasts in the Apocalypse and because there are four corners of the earth. The Church agreed and over the course of many years destroyed the competing Gospels.
From Iranaeus' Against Heresies:
Luckily the religious at that time buried many other Gospels (listed below) in the desert to be stored until they were discovered in the 20th. cent. During the 2nd. cent. there were some 40 - 50 Christian books, many attributed to the disciples of Jesus, including: The Book of Thomas the Contender; The Apocryphon of James; The Gospel of Philip; The Gospel of Thomas, The Gospel of Truth, The Gospel of Judas, The Secret Book of John, The Secret Book of James, The Gospel of Mary, and 40 others found recently at Nag Hammadi, and now in English.
By AD 140, The Gospels of Matthew, Mark, Luke and John, were in use for teaching of clergy. To these four were added the Shepherd of Hermas, The Gospel of Thomas, and the letters from Bishop Clement. And final decision on the canon was not made until AD 397, by the Catholic Bishops.
Bibles into the 5th. cent. included The Shepherd, and letters from Clement, Bp of Rome. The final canon of the NT was not defined until the 16th. cent at the Council of Trent.
All Protestant churches have followed the decision of the Roman Catholic Church on the books to be included in the NT - though not the actual wording approved by the Church.
Bible is the revealed truth from God. New Testament is a record of teachings of Jesus Christ during His ministry which later on, inspired by Holy Spirit, were written down in four Gospels, acts and epistles by His followers. As such it is tantamount to the Word of God. Bible through the inspiration of Holy Spirit was reveal by God Himself and it include the teachings of Jesus who Himself is God. This was clearly told by Jesus:
God used human authors with different backgrounds and personalities to accomplish His purposes through their writing. Each of the gospel authors had a distinct purpose behind his gospel and in carrying out those purposes, each emphasized different aspects of the person and ministry of Jesus Christ. Yet all the four Gospels are perfectly harmonious.
The four New Testament Gospels are like the singers in a four-part choir. They each have their distinct parts to sing, yet the parts combine to make a beautiful composition. Each of the four Gospels gives testimony of Jesus from a slightly different perspective, but they all tell the same story. Thus, they are all in harmony with one another.
Gospel of Matthew was writing to a Hebrew audience, and one of his purposes was to show from Jesus' genealogy and fulfilment of Old Testament prophecies that He was the long-expected Messiah, and thus should be believed in. Matthew's emphasis is that Jesus is the promised King, the “Son of David,” who would forever sit upon the throne of Israel (Matthew 9:27;21:9).
Gospel of Mark was written by Mark, a cousin of Barnabas (Colossians 4:10), was an eyewitness to the events in the life of Christ as well as being a friend of the apostle Peter. Mark wrote for a Gentile audience, as is brought out by his not including things important to Jewish readers (genealogies, Christ's controversies with Jewish leaders of His day, frequent references to the Old Testament, etc.). Mark emphasizes Christ as the suffering Servant, the One who came not to be served, but to serve and give His life a ransom for many (Mark 10:45).
Gospel of Luke,was written by Luke, the “beloved physician” (Colossians 4:14 KJV), evangelist, and companion of the apostle Paul, wrote both the gospel of Luke and the Acts of the apostles. Luke is the only Gentile author of the New Testament. Because he specifically wrote for the benefit of Theophilus, apparently a Gentile of some stature, his gospel was composed with a Gentile audience in mind, and his intent is to show that a Christian's faith is based upon historically reliable and verifiable events. Luke often refers to Christ as the “Son of Man,” emphasizing His humanity, and he shares many details that are not found in the other gospel accounts.
Gospel of John, written by John the apostle, is distinct from the other three Gospels and contains much theological content in regard to the person of Christ and the meaning of faith. The gospel of John begins not with Jesus' birth or earthly ministry but with the activity and characteristics of the Son of God before He became man (John 1:14). The gospel of John emphasizes the deity of Christ, as is seen in his use of such phrases as “the Word was God” (John 1:1), “the Savior of the World” (John 4:42), the “Son of God” (used repeatedly), and “Lord and...God” (John 20:28). In John's gospel, Jesus also affirms His deity with several “I Am” statements; most notable among them is John 8:58, in which He states that “...before Abraham was, I Am” (compare to Exodus 3:13-14). But John also emphasizes the fact of Jesus' humanity, desiring to show the error of a religious sect of his day, the Gnostics, who did not believe in Christ’s humanity.
Thus, in having four distinct and yet equally accurate accounts of Christ, different aspects of His person and ministry are revealed. Each account becomes like a different-colored thread in a tapestry woven together to form a more complete picture of this One who is beyond description. And while we will never fully understand everything about Jesus Christ (John 20:30), through the four Gospels we can know enough of Him to appreciate who He is and what He has done for us so that we may have life through faith in Him.
Like the rest of Scripture, the four Gospels are a beautiful testimony of God’s revelation to man. Imagine a tax collector (Matthew), an untrained Jewish lad with a history as a quitter (Mark), a Roman doctor (Luke), and a Jewish fisherman (John) all writing harmonious testimony about the events in the life of Jesus. There is no way, without the intervention of God, that they could have written these amazingly accurate accounts (2 Timothy 3:16). The historical references, the prophetic references, and the personal details all work together to compose one very detailed, very accurate picture of Jesus—the Messiah, the King, the Servant and the Son of God.
God didn't. The early Church did.
Christianity began as a small group of a few thousand largely uneducated Jewish people which believed in the resurrection of the Lord which expanded to include some Gentiles of like social status around 32 AD. In the years which followed churches centered around the life, death and resurrection of Christ were created largely in the gentile world. The Gospels and Epistles were expressly written to educate believers and convey the spirit of faith love commandments to converts and followers. It is important to remember that most Christians could neither read nor write and it was the job of pastors and other ministry gifts to properly relate the doctrines and correct happenings as held by the God and not necessarily the church. As many errors started in the early church and some perpetuate even today. These errors were largely accidentally but others were spread maliciously.
No church or group of churches ordered the writing or any reversionary books of the Gospels. Instead the Holy Spirit used Holy men of old to write as He inspired. These men were imperfect but they briefly experienced perfection in the relation of the Good News about Christ. Four other people uninspired by the Holy Spirit could have written a historical document based the facts of history relating the life and death of Christ. Their story would be about Christ the spirit which inspired it would be only a human spirit not the Holy Spirit. The Holy Spirit like any writer wrote through men until he expressed all that he wanted to say. It took 4 iterations.
Even with current audio and video recordings allowing preservation of large volumes of material the most effective method of relation is still words recorded in writing as it is already transcribed and searchable. It would be great if we had audio video recordings of Christ and the other writers sermons but even then we would still study the gospels and epistles for they are what the Holy Spirit chose as most important.