Alapiana1 has answered you well, "It wasn't Allah's need to become human and die on the cross for our sins; it was and is our need. It is written, "Without the shedding of Blood there is no remission for sin." God is not willing that any should perish, but that all should come to the knoweldge of truth." I would add my "Amen!" to that and also the following elaboration.
I answered a similar thought voiced by Woodrow a while back. Let me copy and paste it here (I don't have the link to that post):
Christians believe God is fully capable of forgiving each of us with just a thought, or of His own accord. But God has revealed, first in the Old Testament, that to be just God must punish every sin. So He instituted the animal sacrifice system and, for example, a lamb without spot or blemish was sacrificed for the sins of the people. There were probably millions of animals sacrificed over the hundreds of years they did that. Why? Because:
Lev. 17:11 "For the life of the flesh is in the blood, and I have given it to you upon the altar to make atonement for your souls; for it is the blood that makes atonement for the soul."
Now the blood of those animals merely covered sins, as in the Passover, when God saw the blood, He would pass over the sinner and judgment would not fall on him. The sin was paid for by the animal's life, its blood. God's MERCY on the sinner was based on the shedding of blood of the animal in payment for the sinner's sins.
All of that was a type or picture of the Ultimate Sacrifice to come when Jesus, "the Lamb of God who takes away the sin of the world" (John 1:29) would lay down His life, shedding the "precious blood of Christ, as of a lamb without blemish and without spot" (1 Peter 1:19). But Christ's blood doesn't just cover sins, it washes they away (Rev. 1:5; 1 John 1:7).
That is now the basis of a person's redemption and of God's mercy and grace toward the sinner. That is God's way. For a sinner to say to God, "No, I reject what Christ did for me," is to reject GOD'S way of salvation, which then removes any chance for mercy and forgiveness. God "spared not His own Son but delivered Him up for us all" (Rom. 8:32). In effect, God sent His Son to save the world by His shed blood, showing HIM no mercy as He (Jesus) bore our sins (taking our punishment), so that God could be JUST in terms of punishing all sin, and show US mercy by giving us forgiveness as a free gift. And because it is free to us, we have no excuse. If we reject it, we simply sentence OURSELVES to an eternity paying for our own sins.