Shaykh al-Islām Ibn Taymiyyah (d. 721 AH) said:
Regardless of whether the Christians choose to testify that Muḥammad (صلى الله عليه وسلم) had spoken the truth or that he (صلى الله عليه وسلم) lied, it necessitates the falsification of their own religion in both instances.
If he was a truthful prophet, then he has delivered from Allāh, as related in several places in this book [i.e. the Qurʾān], that the Christians have disbelieved. Hence, he has called them to believe in him and has ordered the Muslims to struggle against them [in calling them to the straight path and fighting them when it is lawful to do so]. So whoever knows that he (صلى الله عليه وسلم) was a prophet, even if only to a specific group of people, it would still obligate believing in everything that prophet had related. He (صلى الله عليه وسلم) has related that the Christians are misguided and have disbelieved. Considering this, their use of intellectual arguments or any passage from their books in support of their religion are all completely futile. Rather, it is a well-established fact that all the evidence they use to support their religion being the truth are generally false anyways, even if the corrupt nature of their individual evidences are not clarified in detail. This is because all of the prophets only speak the truth. Likewise, when the Messiah (عليه السلام) judged the Jews as having disbelieved when they labelled him a liar, anything the Jews could use to prove to the contrary must be false. Thus, anything that opposes the unerring speech of the Prophet Muḥammad (صلى الله عليه وسلم) is completely false.
Alternatively, if they claim that Muḥammad (صلى الله عليه وسلم) generally lied in speech, without exception, and they claim: He was never a prophet, nor was he sent to anyone, not the Arabs or other than them. Rather, he was a liar. Considering this claim, they prevent themselves from believing in the prophethood of anyone else. This is because the same methodology with which the prophethood of Musá and ʿĪsá is confirmed can be used to confirm the prophethood of Muḥammad (صلى الله عليه وسلم). Rather, this methodology is more clear, evident, and potent in its application to him (صلى الله عليه وسلم) than them.
In clarification of this, if they were to say: We know the prophethood of Mūsá and ʿĪsá by means of the miracles they performed. These miracles are related to us through several independent lines of inquiry. We would say:
The miracles of the Prophet Muḥammad (صلى الله عليه وسلم) are greater, its narration is stronger and more authentic, the book that Muḥammad (صلى الله عليه وسلم) has brought is more complete, his ummah is superior, and the legislations of his religion are more replete with goodness. For Mūsá came with justice, and ʿĪsá came with bounties and blessings that completed and perfected that justice. While he (صلى الله عليه وسلم) has combined in his legislation between the justice [of Mūsá] and the bounties [of Īsá].
Thus, if it could ever be permissible for someone to say: He (صلى الله عليه وسلم), in spite of this, was still a lying slanderer. Then, based on this false foundation, it would be even more befitting to allege the same thing for someone other than him. Thus, by disbelieving in Muḥammad (صلى الله عليه وسلم), they have essentially falsified the prophethood of anyone else they claim as prophets. As the ruling granted to one of two similar persons must logically be granted to the other. What, then, should be said if the prophethood of one of those persons is more apparent than his counterparts?
If someone was to then say: Indeed, Aaron, Yūshaʿ, David, and Soloman were all prophets, but Mūsá or ʿĪsá were not. Or make the claim of al-Sāmarrah1 that Yūshaʿ was a prophet but those after him like David, Soloman and the Messiah were not. Or to claim what the Jews claim that David, Solomon, Ashʿiyā, Ḥabqūq, Malīkhā, ʿĀmūṣ, and Daniel2 were all prophets but the Messiah was not. All of these claims represent contradictory statements and clearly apparent falsehood. This is because those whose prophethood have been rejected are more deserving of it, their prophethood more complete and perfect than those who have been confirmed as prophets. These more complete prophets possess even greater evidence as to their prophethood than the rest of them. How, then, could it be permissible to confirm the prophethood of the less magnanimous among them while rejecting the prophethood of the best of them? This is similar to if someone was to say that Zufar, Ibn al-Qāsim, al-Muzanī, and al-Athram were all jurists but Abū Ḥanīfah, Mālik, al-Shāfiʿī, and Aḥmad were not. Or to claim that al-Akhfash, Ibn al-Anbārī, and al-Mubarrad were all experts of language but al-Khalīl, Sībawayh, and al-Farrāʾ were not.
Thus, the claim that David, Solomon, Malīkhā, ʿAmūṣ, and Daniel were all prophets but Muḥammad ibn ʿAbdullāh (صلى الله عليه وسلم) was not represents a contradiction that is even more clear than that. The corruption in such a claim is even more apparent. Just as if someone was to claim that Mūsá and ʿĪsá were prophets and that the Tawrāh and the Injīl were books revealed from Allāh, but Muḥammad (صلى الله عليه وسلم) was not a messenger and the Qurʾān was not revealed from Allāh. The inherent falsehood in this claim is plainly evident and clear for the one who truly contemplates what Muḥammad (صلى الله عليه وسلم) and those before him came with, and contemplates his book and the books of those before him, and the signs of his prophethood and the evidence of their prophethood, and the legislations of his religion and those of their religion.
For they [the Jews and Christians] did not bring a single piece of evidence that ascertains the truthfulness of those among the prophets they use as evidence. Such that if they were to argue with those who disbelieve in all of the prophets like the polytheists and atheists, they have nothing that could be used to support their argument. Just as they lack any evidence in their arguments against the Muslims who testify as to the prophethood of all of the prophets. As the consensus of Muslims only know of their prophethood because Muḥammad (صلى الله عليه وسلم) related that they were prophets. Logically, they would be prevented from believing in the branches [i.e., these other prophets] were they to question the validity of their foundation [i.e. Muḥāmmad (صلى الله عليه وسلم)] by which they recognise the truthfulness of those other prophets [Herego, the Jews and Christians’ rejection of some prophets and confirmation of others stipulates rejection of the ones they confirmed just as if the Muslims were to reject some and confirm others like them].
 Al-Sāmarrah: Jewish sect that, unlike the rest of the Jews, believes in the prophethood of Mūsá, Aaron, and Yūshaʿ but rejects the prophethood of anyone after them. They differ from the rest of the Jews in other ways as well, including possession of their own version of the Torah, not recognising the Holy Land, speaking a different language than the rest of the Jews, and in other ways. See Tafsīr al-Ṭabarī 2:66.
 Note: all prophets mentioned here are related in Jewish sources but are not spoken about in as much detail as the Messiah. To take them as prophets but reject the prophethood of the Messiah is contrary to reason and logic. This is the point being made here.
Source: al-Jawāb al-Ṣaḥīḥ 2:21-28
Translated by: Riyāḍ al-Kanadī