Summary of answer:
Praise be to Allah
There is nothing in the Holy Qur’an or in the Prophet’s Sunnah to condemn the early Christians (i.e., before the sending of our Prophet Muhammad (blessings and peace of Allah be upon him)) as disbelievers because of their belief that the Messiah (peace be upon him) was killed and crucified. Rather Allah, may He be glorified and exalted, condemns them as disbelievers because they regarded the Messiah as a god, and because they regarded divinity as being three: Father, Son and Holy Spirit.
Allah, may He be exalted, says (interpretation of the meaning):
“Surely, they have disbelieved who say: ‘Allah is the Messiah (‘Eesa (Jesus)), son of Maryam (Mary).’ But the Messiah (‘Eesa (Jesus)) said: ‘O Children of Israel! Worship Allah, my Lord and your Lord.’ Verily, whosoever sets up partners in worship with Allah, then Allah has forbidden Paradise for him, and the Fire will be his abode. And for the Zalimoon (polytheists and wrongdoers) there are no helpers.
Surely, disbelievers are those who said: ‘Allah is the third of the three (in a Trinity).’ But there is no ilah (god) (none who has the right to be worshipped) but One Ilah (God -Allah). And if they cease not from what they say, verily, a painful torment will befall the disbelievers among them”
There is nothing in the Holy Qur’an that says “surely they have disbelieved who say that the Messiah was killed and crucified”!
The reason for that is that Allah caused another man to resemble ‘Eesa, and his enemies killed him, thinking that he was the Messiah. Not one of the followers of the Messiah and his disciples was present in that place, so that they could be certain of the identity of the one who was crucified, apart from some women who stood some way off, looking on. Then the news spread that the Messiah had been killed and crucified and buried, and many people believed that, even some of his followers, because they did not have knowledge to prove that false, and the Messiah – as he was a human being – could have been killed, as the Jews had killed other Prophets before him.
That was the excuse of those who adopted this false belief.
Hence we agree with your view that it is natural – as you say – that the Christians, by whom we mean the early Christians, before the coming of our Prophet (blessings and peace of Allah be upon him) would believe in the crucifixion and the killing of ‘Eesa (peace be upon him). But after the sending of the Messenger (blessings and peace of Allah be upon him) and the revelation of the Qur’an, and the definitive denial of the killing and crucifixion of the Messiah, whoever believes in the killing and crucifixion of the Messiah after that is a disbeliever, because he has rejected what Qur’an says, which definitive evidence and miracles have proven is the true word of Allah and not the words of any human being.
Whoever among the followers of the Messiah – before the Prophethood of our Prophet Muhammad (blessings and peace of Allah be upon him) – believed in the Messiah as a Prophet and Messenger, not as a god or son of God, and followed his teachings, but mistakenly believed that he was killed and crucified, that person was a believer and a monotheist, and is excused for that mistaken belief.
Ibn Taymiyah (may Allah have mercy on him) said:
If it is said that the disciples, or some of them, or many of the people of the Book, or most of them, used to believe that the Messiah himself was crucified, they were mistaken in that, but this mistake was not something that would undermine their belief in the Messiah, if they believed in what he brought, and they are not inevitably doomed to Hell, because the Gospels that are in the hands of the People of the Book mentioned the crucifixion of the Messiah.
End quote from al-Jawaab as-Saheeh (2/302)
But that excuse ceased with the coming of the true facts from the Lord of the Worlds, in His Book, that the matter was made to appear thus to the Jews, and that Allah, may He be glorified and exalted, did not give them power over the Prophet of Allah ‘Eesa in any real sense, and He did not enable them to kill him or crucify him. As that is the case, there is no longer any excuse, once the true facts have come.
Ibn Hazm (may Allah have mercy on him) said:
Allah, may He be glorified and exalted, did not send down any book before the Qur’an in which it was either affirmed or denied that the Messiah (blessings and peace of Allah be upon him) was crucified; rather it was confirmed in the Qur’an that this never happened, thus is became required to reject the reports which said that he was crucified.
End quote from al-Fasl fi’l-Milal wa’l-Ahwa’ wa’n-Nihal (1/57)
But the facts mentioned in the Holy Qur’an only benefit those who hear it and receive it on the basis of proof that leaves no excuse, and those for whom proof is established of the Prophethood of our Prophet (blessings and peace of Allah be upon him) and the truthfulness of his message.
Therefore it is appropriate here to call the Jews and Christians to Islam and to believe in Muhammad (blessings and peace of Allah be upon him) as a Prophet and Messenger from Allah, may He be exalted, and to believe in the Qur’an as the word of Allah, may He be glorified and exalted. Whoever submits in Islam to Allah, the Lord of the Worlds, and believes in His Prophet, and in His holy Book, it becomes to him, on the basis of rational thinking, to believe in the words of Allah, may He be glorified and exalted, concerning this matter (interpretation of the meaning):
“And because of their saying (in boast), ‘We killed Messiah ‘Eesa (Jesus), son of Maryam (Mary), the Messenger of Allah,’ - but they killed him not, nor crucified him, but the resemblance of ‘Eesa (Jesus) was put over another man (and they killed that man), and those who differ therein are full of doubts. They have no (certain) knowledge, they follow nothing but conjecture. For surely; they killed him not (i.e. ‘Eesa (Jesus), son of Maryam (Mary) )
But Allah raised him (‘Eesa (Jesus)) up (with his body and soul) unto Himself (and he is in the heavens). And Allah is Ever AllPowerful, AllWise”
[an-Nisa’ 4:157, 158].
What is so hard to believe in what the Qur’an mentions? Especially since we are speaking about a Prophet and Messenger such as ‘Eesa (peace be upon him), who used to raise the dead and heal those born blind and lepers, and who spoke in the cradle, all of which are miracles that are contrary to the laws governing the universe and human beings. So why would we find it far-fetched to believe that Allah, may He be glorified and exalted, would make the man who was crucified resemble ‘Eesa to those who were present at the crucifixion? What is so impossible about this fact? Allah, may He be glorified and exalted, supports His Messengers, and protects them by His grace and might, so that ‘Eesa was kept with Allah for a mission at the end of time.
Hence the Muslim should not speak to the Christian about the crucifixion in the first place, and debate with him as to whether it happened or not, except from the angle of purely historical discussion of the issue. But with regard to establishing religious proof that Islam is more deserving of being followed, and that it abrogates what came before it, then debating the crucifixion is not of any benefit. Rather the journey to knowledge should begin with reflecting upon the Oneness of Allah, may He be glorified, then the Prophethood of the final Messenger, Muhammad (blessings and peace of Allah be upon him). Then whoever rejects these two fundamentals will be more likely and more keen to reject others, and whoever believes in them will be more keen to believe in what the Qur’an teaches about the crucifixion.
If a person believes in the words of Allah, then the Muslim can look again at the crucifixion from a historical point of view, in the light of the definitive negation in the Holy Quran of the notion that the Messiah (peace be upon him) was killed and crucified at the hands of his enemies. He will discover that talking about having seen things with their own eyes – as mentioned in question – is subject to further discussion and investigation. No one possesses any historical texts, supported by solid chains of transmission or large numbers of reports, that contain accounts from those who saw the crucifixion with their own eyes, and we do not have anything to confirm eyewitness reports of the crucifixion. The Qur’an confirms that someone else was made to resemble him to those who had conspired against him, but it does not speak of unbiased eyewitnesses or say that it was made to appear to the followers of the Messiah (peace be upon him) that he was crucified. The Gospels that are available in print nowadays do not mention anything but the testimony of a few women who saw the scene from afar, not from up close, so it is not far-fetched to say that the matter was made to appear thus to them too. Such testimony from afar does not reach the level of reliability that some people think it does.
Imam as-Sarkhasi (may Allah have mercy on him) said:
What they quote as evidence of reports from the Jews and Christians about the killing and crucifixion of the Messiah is an illusion, because there are no reliable and widely reported accounts concerning that.
The Christians only narrated that from four individuals who were with the Messiah in a house, because the disciples had gone into hiding or scattered when the Jews wanted to kill them.
The Jews only transmitted that from seven individuals who had entered the house where the Messiah was, and it is possible that those people had come to an agreement to tell a lie. It was narrated that they did not really recognise the Messiah until a man called Judas pointed him out to them, who had been his companion before that… This is not widely report and does not reach the level of reliability.
If it is said: The crucifixion was witnessed by a group of people who it cannot be imagined would ordinarily agree to tell a lie, thus it is established that the accounts of the crucifixion were widely reported and reliable,
Our response is: No, that is not the case. The matter of the crucifixion was only narrated by a small number of people, then all the people who narrated it from them said that the one who was crucified was So and so, but they were looking at him from afar, without looking closely at him, because naturally people would be averse to looking closely at one who was being crucified… Secondly, the widely-reported account that speaks of the killing and crucifixion of a man they called ‘Eesa may reach the level of certainty, but the man was not ‘Eesa; rather he was caused to look like him, as Allah, may He be exalted, says (interpretation of the meaning): “but the resemblance of ‘Eesa (Jesus) was put over another man” [an-Nisa’ 4:157]. It is narrated that ‘Eesa (peace be upon him) said to those who were with him: Whoever among you would like to meet Allah, he will be made to resemble me and be killed, and Paradise will be his. A man said: I will do that. So Allah caused him to resemble ‘Eesa and he was killed, and ‘Eesa was taken up into heaven.
End quote from Usool as-Sarkhasi (1/285-286)