Jesus did warn us of fasle prophets:
15 Beware of false prophets, who come to you in sheeps clothing, but inwardly they are ravenous wolves. 16 You will know them by their fruits. Do men gather grapes from thornbushes or figs from thistles? 17 Even so, every good tree bears good fruit, but a bad tree bears bad fruit. 18 A good tree cannot bear bad fruit, nor can a bad tree bear good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 Therefore by their fruits you will know them. ---Matthew 7
Sounds exactly like the murderer and pedophile Muhammed, as well as all his followers. Look at the fruits of his false religion...suicide bombers, cowardly thugs who decapitate people in their name of their false god. Nothing good has ever come from Islam, because the root of it is evil and false.
Actually I was thinking the exact same thing but I was looking more at Mathew 24:23-25
23Then if any man shall say unto you, Lo, here is Christ, or there; believe it not.
24For there shall arise false Christs, and false prophets, and shall shew great signs and wonders; insomuch that, if it were possible, they shall deceive the very elect.
25Behold, I have told you before.
Clearly Jesus did foretell the comming of Mohammad,not as a Prophet but as a false Prophet.