[QUOTE=islamispeace] The doctrine is absent from the OT. It was invented by Christians centuries after Jesus (pbuh). [/QUOTE]
The very name of God is plural in the OT. אלהים (Elohim) has the masculine plural ending "im" does it not? Ever wonder why?
Gen 1:26 says:
ויאמר אלהים נעשה אדם בצלמנו כדמותנו
Then God said, "Let Us make man in Our image, according to Our likeness"
God = אלהים (Elohim)
said = אמר (Amar) in the singular
make = עשה (asah) is in the plural and "in our image" and "after our likeness" בצלמנו כדמותנו (betsalmenu, kidmutenu) have the 1st person plural suffix נו(nu).
Note the mixture of singular and plural. God is a singularity that is also a plurality. This the God presented in the Hebrew Bible. אלהים (Elohim) plural is אחד (echad) singular.
More examples can be adduced. The doctrine of the Trinity is in both the OT and the NT but is clearly denied in the Quran. Thus the Quran is not a revelation from God.