Luke 23:40But the other criminal rebuked him. "Don't you fear God," he said, "since you are under the same sentence? 41We are punished justly, for we are getting what our deeds deserve. But this man has done nothing wrong." 42Then he said, "Jesus, remember me when you come into your kingdom.[a]"
Where does the man ask for forgiveness?
Luke 23:40But the other criminal rebuked him. "Don't you fear God," he said, "since you are under the same sentence? 41We are punished justly, for we are getting what our deeds deserve. But this man has done nothing wrong." 42Then he said, "Jesus, remember me when you come into your kingdom.[a]"
I'm not sure exactly what you are asking, but you seem to be implying that the thief was forgiven even though he never asked to be forgiven. Therefore, God (or whomever) can forgive a murdering Muslim even thought he doesn't ask for forgivenenss. Is this your arguement? I can certainly answer, but I want to make sure I answer what you are asking. For now, I'll assume this is your assertion and go ahead and answer. If I have not understood your question you can object and I'll try again.
In Matthew 28 we are told how Jesus was mocked and reviled, not unlike many treat Him today. In 28:44 we are told that the robbers who were crucified with Him 'also reviled Him in the same way.' Yet in Luke 23 we see one of the robbers suddenly sided with Jesus, declared his own guilt and confessed that Jesus had done nothing wrong. What's going on? At some point during the crucifixion, the robber was regenerated and given the gift of faith, his understanding was opened and he recognized the truth about what was going on and was made able to confess the truth about Christ and himself. In other words, the thief came to faith, he was converted. One of the results of faith is justification, the forgiveness of sin. This is an example of justification by faith, justification includes forgiveness.
The thief did the work of the Father which is this "...that you believe in Him whom He [the Father] sent." John 6:28.
The thief on the cross demonstrates salvation by grace alone through faith alone in Christ alone to the glory of God alone. Lest any man should boast. To those of you who are certain that this is wrong and that you must supply works of righteousness which God will graciously accept, I point you to Matthew 7:21-23, and remind you that the will of the Father in Heaven is stated in John 6:28.
If a murdering Muslim confesses his guilt, as the thief did, and repents of his rejection of Jesus, as the thief did, and does the work that the Father gives us to do, as the thief did, then the Muslim will be forgiven (and of course he will no longer be a Muslim). Otherwise he will die in his sins.