Deuteronomy 13 warns against a prophet or dreamer who uses a sign to call people to "other gods." That is a serious monotheistic test, but it is not the same as Paul's "angel from heaven" warning in Galatians 1, and it is not a test that Prophet Muhammad (PBUH) fails. His mission was to destroy idolatry and call humanity to the Creator worshipped by Abraham, Moses, and Jesus.
What Deuteronomy 13 Actually Says
The passage is not a general "angel test." It speaks about a prophet or dreamer with a sign or wonder who then calls people to worship other gods:
"If there arise among you a prophet, or a dreamer of dreams, and giveth thee a sign or a wonder... saying, Let us go after other gods, which thou hast not known, and let us serve them; thou shalt not hearken unto the words of that prophet, or that dreamer of dreams..."
Deuteronomy 13:1-3
The explicit mark of falsehood here is a call to apostasy and idolatry: "Let us go after other gods." It is not simply "a later prophet differs from my current interpretation of scripture in legal details." If the test were "no later dispensation may alter any Mosaic ruling," it would also create a problem for mainstream Christianity's own claim that many Mosaic covenantal rulings are no longer binding in the same way after Jesus. The issue in Deuteronomy 13 is loyalty to the one God, not mere difference in law.
Muhammad (PBUH) Called to the God of Abraham, Not to Other Gods
From the Muslim perspective, Prophet Muhammad (PBUH) did exactly the opposite of what Deuteronomy 13 condemns. He rejected idols, abolished pagan worship in Arabia, affirmed the prophets of Israel, and called people to Allah, the Creator and Lord of Abraham, Ishmael, Isaac, Jacob, Moses, and Jesus. Christians will dispute the Quran's account of God and Christ, but that is a different theological dispute; it should not be smuggled into Deuteronomy 13 as though Islam were calling to Baal, Zeus, or an unknown rival deity.
And We sent not before you any messenger except that We revealed to him that, "There is no deity except Me, so worship Me."
Quran 21:25
Say, "O People of the Scripture, come to a word that is equitable between us and you - that we will not worship except Allah and not associate anything with Him and not take one another as lords besides Allah." But if they turn away, then say, "Bear witness that we are Muslims [submitting to Him]."
Quran 3:64
The Quran as Confirming and Judging Previous Revelation
Islam's answer is not that any claimed revelation should be accepted untested. Rather, the Quran presents itself as the final revelation: confirming the truth Allah revealed before it, correcting distortions and disputed interpretations, and serving as the criterion over previous scripture. Muslims therefore do not treat the later Jewish or Christian canon, or a particular church reading of it, as an authority above the Quran.
And We have revealed to you the Book in truth, confirming that which preceded it of the Scripture and as a criterion over it... To each of you We prescribed a law and a method.
Quran 5:48
This matters because Islam distinguishes between the original revelations given to Moses and Jesus and the later textual transmission and theological interpretation of those communities. The Quran does not deny Moses or Jesus; it claims to restore their pure monotheistic call.
Do Not Confuse Deuteronomy 13 with Galatians 1
The "angel from heaven" wording belongs to Paul's letter to the Galatians, not to Deuteronomy:
"But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed."
Galatians 1:8
A Christian may appeal to Galatians from within the Christian canon. But as an argument against Islam, using specifically Pauline doctrine as the unargued test of Muhammad (PBUH) is circular: it assumes Paul's authority and Paul's formulation of the gospel, precisely points that Islam does not grant. The Muslim position is that Jesus preached worship of the one God and submission to Him, and that later claims about divine sonship, incarnation, and atonement are not the standard by which God's final messenger is judged.
The Moral and Monotheistic Substance
When Muhammad's actual message is examined, it is not a summons to moral corruption or polytheism. It commands worship of one God alone; prayer, charity, fasting, truthfulness, chastity, justice, mercy, care for parents, kin, orphans, and the poor; and it forbids murder, adultery, theft, oppression, false testimony, and idolatry.
Indeed, Allah orders justice and good conduct and giving to relatives and forbids immorality and bad conduct and oppression. He admonishes you that perhaps you will be reminded.
Quran 16:90
This is why the Deuteronomy 13 objection fails on its own stated terms. Muhammad (PBUH) did not say, "Let us go after other gods." He said, in continuity with the prophets, "There is no deity except Allah." The real disagreement between Islam and Christianity is not whether idols should be worshipped; it is whether later Christian doctrines about God and Christ are the final standard over revelation. Islam answers no: the Quran is the final criterion, and its call is uncompromising tawhid.
For related discussions, see the questions of the Injil, the preservation of previous scriptures, and Paul's warning in Galatians 1.