"The Deuteronomy Deductions: Two Short, Sound, Simple Proofs that Muhammad Was a False Prophet"
To grasp the force of the proofs, you'll need to read the article. However, I can give you the gist of the argument here. Consider the following quotations, one from the Bible, and one from Islam's History of al-Tabari.
"But the prophet who speaks a word presumptuously in My name which I have not commanded him to speak . . . that prophet shall die." ~GOD (Deuteronomy18:20)
"I have fabricated things against God and have imputed to Him words which He has not spoken." ~MUHAMMAD (Al-Tabari 6:111)
According to the first quotation, a prophet who delivers a message that does not come from God is not a true prophet. In the second quotation, Muhammad says that he has delivered a revelation that did not come from God!
The passage in al-Tabari refers to the infamous "Satanic Verses"--one of the most embarrassing moments in Muslim history. According to numerous ancient Muslim sources, Muhammad delivered verses that came, not from God, but from Satan. (For more on this, see "Muhammad and the Satanic Verses.")
One might object that Muslims typically believe that the Bible has been corrupted, and that a criterion taken from Deuteronomy is therefore irrelevant. On the contrary! The verse is Deuteronomy 18:20. Those familiar with Muslim apologetics will recognize this as the verse that follows Deuteronomy 18:18-19, one of the most frequently quoted passages among Muslims. This is the passage where God declares that he will send another prophet like Moses. Muslims appeal to this as their strongest biblical support for the prophethood of Muhammad. Yet, if they're going to appeal to 18:18-19 as inspired, surely they cannot reject 18:20!
But if Muslims are stuck with 18:20, they must either admit that Muhammad was a false prophet, or they must show that Muhammad never delivered the Satanic Verses. Muslims will obviously opt for the latter course, but they can only do so by throwing out nine of their own sources! Throwing out so many of their own sources, however, simply serves as proof that Muslims are not examining their records objectively. Instead, they are picking and choosing the texts that make them feel best.