The Bible declares that the clear indication of whether one who claims to be a prophet is in fact not a true prophet of God is if he contradicts what the Bible teaches (Isaiah:8:20To the law and to the testimony: if they speak not according to this word, it is because there is no light in them.
See All... [1]). By that criterion, both Muhammad and Baha'u'llah (as well as Buddha, Krishna, et al.) are false prophets, because they clearly contradict the teachings of Jesus and His apostles, who built without contradiction upon the teachings of the Old Testament prophets. —TBC

"To the law and to the testimony: if they speak not according to this word, it is because there is no light in them." —Isaiah:8:20To the law and to the testimony: if they speak not according to this word, it is because there is no light in them.
See All... [1]