2 Timothy 3:16-17 esv
16 All Scripture is breathed out by God and profitable for teaching, for reproof, for correction, and for training in righteousness, 17 that the man of God may be complete, equipped for every good work.
I believe that the original scriptures are sufficient and, as Paul wrote, "complete". Accordingly, the original scriptures are all that one needs, according to Paul. Therefore, and speaking only for myself, I am skeptical of believing doctrines that came about long after the writings of the original apostles and their disciples. Paul actually warned against this. For instance:
Galatians 1:8 esv
But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.
Maybe Mohammad should have followed what Paul wrote about angels preaching things that were contrary to the "gospel".
Surah 96: The Clot (96:1-5)
This short passage consists of the very first words that were revealed to Muhammad in the cave outside of Mecca. When Muhammad was forty years old, he went to Mt. Hira, outside of Mecca, to have a spiritual retreat by himself. During the night, the Angel Gabriel appeared to him and spoke these words to him...