**TomazsA, please understand that Jesus could not die within a short time. he was a healthy stout person. When brought down, the other two thieves were alive. So how could Jesus be dead. He had simply fainted on the cross and appeared to all as a dead man.
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There are numerous problems with this. The first problem is that the Qur’an says Jesus was not crucified, period. You seem to be saying He was crucified but survived, this doesn’t square with the aya nor does it coincide with the traditional belief of a substitution (i.e. Judas getting crucified).
You speak of Jesus being unable to die so soon, I think you have to realize that He was on the cross for several hours and this was after being severely scourged and carrying the cross. Ultimately Christ’s own life was in His hands and He gave it up willingly.
If Jesus had fainted, one wonders how no one realized. No one realized when He was taken down from the cross, Joseph of Arrymathea didn’t realize when he laid Christ in the tomb, nor did Jesus realize when He came walking out of the tomb three days later! This makes the idea of fainting difficult to accept.
How do we know Jesus was dead? We know because Jesus’ disciples saw Him take His last breath. Likewise, when the guards were ordered to break the legs of the Crucified to speed up their death, they found Jesus dead already. To insure He really was dead, the centurion pierced Jesus’ side.
So with all this we are certain Jesus was dead.
Moreover, God did not want Jesus to die on the cross, a cursed death planned by his opponents. God had told Jesus during his prayer in garden that he will not die on the cross. An angel (H.S.) had come to support Jesus to tell him that his prayer was accepted. Angel did not come to tell Jesus that his prayer is not accepted. Jesus was praying to avoid the cup. he wanted his apostles to pray too. He was happy when he was assured by God.