Allah sent down many Divine Books to His Messengers (may Allah be pleased with them all) to lead mankind to the path of truth, and guide them to worship Him and shun polytheism and vice.
He Almighty revealed the Scriptures to Abraham, the Torah to Moses, the Psalms to David, the Gospels to Jesus, and the Qur’an to Muhammad (peace and blessings be upon them all).
Some of those Divine Books were revealed in the form of scriptures such as the Torah. Allah Almighty says, “Then, when the anger of Moses abated, he took up the tablets, and in their inscription there was guidance and mercy for all those who fear their Lord.” (Al-‘A`raaf: 154).
And some were revealed in the form of admonitions and advice such as the Gospel.
It stands to reason that Jesus (peace and blessings be upon him) was not illiterate. He was highly educated and was well-read. However, he used to communicate his teachings to his disciples in the form of oral form rather than written form. The disciples, in turn, used to remember what Jesus taught them off by heart.
When Jesus (peace and blessings be upon him) ascended to heaven, all his advice and teachings were known to his disciples. Unfortunately, they were not good at memorizing, and not all were able to comprehend Jesus’ teachings. Most probably, this was the main reason behind the distortions that took place following his ascension (peace and blessings be upon him).
Moreover, the Roman Empire and the Jews were brutal opponents of Christians at that time. They mercilessly killed Christians causing a detrimental effect on the recording of the Gospel as most of those who memorized it were tortured and killed.
Allah Almighty says: “And with those who say: “Lo! we are Christians,” We made a covenant, but they forgot a part of that whereof they were admonished. Therefore We have stirred up enmity and hatred among them till the Day of Resurrection, when Allah will inform them of their handiwork.” (Al-Ma’dah: 14)
As for compiling the Gospel and classifying it in volumes, the oldest known version came to being 80 years after the ascension of Jesus (peace and blessings be upon him). This means that there were three generations that do not know anything about the Gospel being in a written form. Also, none of the disciples or their successors attempted to compile the teachings of Jesus in written form. This may serve as a primary cause behind the noticeable distortions.
Instead of concentrating on the Oneness of Allah, and following in the footsteps of Allah’s Prophets and Messengers, the founder of the Pauline Church, St. Paul (Saul), began to preach the concept of the Trinity and hence moved far from the original Gospel.
Such distortions have dramatically led to decay and incomprehension in the teachings of Jesus (peace and blessings be upon him).
It is clear that Allah sent down the Gospel to Jesus (peace and blessings be upon him), but his disciples did not take an active role in preserving it as Muslims did with the Qur’an, which was revealed to Prophet Muhammad (peace and blessings be upon him), who ordered Muslims to write it down. It was dictated under his supervision.
Considering all this, we thank Allah Almighty that He has guided the Muslim Ummah to preserve the Ever-Glorious Qur’an. Allah Almighty says, “Lo! We, even We, reveal the Reminder, and lo! We verily are it’s Guardian.” (Al-Hijr: 9)”