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The Qur'an is quite accurate when it says in 4:157 that they have no "sure knowledge" of the event and that they are following "assumptions".
That's because of this verse:
"The man who saw it has given testimony, and his testimony is true. He knows that he tells the truth, and he testifies so that you also may believe.” - John 19:35.
This is the only verse in the four gospels where one witness is at the very least, supposed to be the only person from start to finish to have seen the crucifixion event.
We run into two stumbling blocks though. Codex Palatinus (6th century) and Codex Fuldendis (4th/5th century). Both are in Latin and omit the verse entirely.
The earliest surviving manuscripts with John 19 would be from the 4th century onwards, these would be codices Sinaiticus, Alexandrinus, Vaticanus, etc. These were written in Greek. There's a problem though.
These 3 Greek codices we cannot say for certain under whose authority they were written, and they themselves have variants in this passage which I'll cover later. We do know however that under the Emperor's command, Jerome with the Church's authority was commissioned to produce an official Latin version of the Bible, which is why we can say with the Church's authority the verse is actually absent.
It should also be explained that the Latin text was translated from the Greek, and so it stands to reason that the Greek version the two aforementioned Latin versions were produced from, stand to either be contemporaneous
Lastly, as I mentioned above there is a variant in the Greek for this passage where the audience to whom it was written changes. In one version it reads "so that you may believe", meaning then that the passage was written to convince you of converting to Christianity, but another variant reads "that you may continue to believe", being then written for someone who already believes to give them confidence of faith.
There's a lot to unpack here, but the Qur'an's precision with the Bible's dubious history is frankly, unprecedented. In other words, the New Testament's only verse attesting to a witness for the entire time of the crucifixion is either made up or highly unreliable in and of itself.
