Was Muhammad a true prophet?

No - measured both by the reliability of the sources for his prophetic claim and by the Christ those sources deny, the claim does not hold. The honest starting point, though, is that Muhammad was a real historical figure, not a myth. He preached in early-seventh-century Arabia and founded the movement that erupted out of Arabia within a few years of his death in 632; to deny that would badly overreach the evidence, and the scholarly revisionism that tried it in the 1970s was largely rolled back.

Testing a claim to prophethood means examining the sources, and here honesty is needed. Almost none of the vivid detail - the angel in the cave of Hira, the wording of particular sermons, the miracle reports - comes from the Quran, which says remarkably little about his life. It comes from the sira, the prophetic biography. The earliest, by Ibn Ishaq, was written roughly 120 to 135 years after Muhammad died, survives only through a later editor (Ibn Hisham) who tells us he left out what might 'distress' people, and rests on a tradition its own scholars did not treat as beyond question.

So the granular portrait should be held loosely. Ask for a single, even standard applied to both faiths' founding sources, and the New Testament - resting partly on eyewitness testimony, and behind it the creed of 1 Corinthians 15:3-7 datable to within a few years of the crucifixion - stands far closer to its events than the sira stands to Muhammad. But the deeper test is not only about dates: a true prophet confirms God's prior revelation rather than contradicting it (Galatians 1:8), and Muhammad's message denies its very heart - the deity of Christ, his death on the cross, and his resurrection. So the honest verdict is no: by both measures - the late and theologically shaped sources for his prophethood, and the risen Christ his message contradicts - Muhammad cannot be received as a true prophet of God. That is not a weapon to wield over anyone made, as we all are, in the image of God. It is said with gentleness and respect (1 Peter 3:15), as an invitation to follow the evidence together to the One it keeps pointing to.