Some Muslim critics of Christianity attack the power of the Christian God by stating that he is too weak to forgive a person's sins without the shedding of blood. These critics often say that if the Christian God is so powerful, then why can't he declare a person to be forgiven without requiring a blood sacrifice? They sometimes view this as a weakness in the Christian concept of God. But this is not a weakness. It is a declaration of the holiness of Yahweh and the lack of holiness of the God of Islam.
In Christianity, God is far too holy to accept the sincerity and repentance of a person so as to forgive that person of his or her sins. But in Islam, a person's sincerity and repentance are sufficient to warrant forgiveness per Allah's grace. Why the difference? The difference is due to the fact that God has revealed in the Bible that his Holiness is so complete and so perfect, and that our sinfulness is so pervasive, that even our sincerity and our repentance are touched by sin and are not acceptable to God. In other words, sin has touched all of what we are: our hearts, our minds, our intentions, our wills, our emotions, etc. For a Muslim to say that God can forgive a person because the person is sincere, is to appeal to God based upon the goodness of the person; namely, his sincerity of heart. This assumes that a person can be good enough to please God. Apparently, this is the Islamic position that people are capable of being good enough to please God on their own efforts. By contrast, it is not the view of Christianity because the great gulf between God's infinite holiness and man's sinfulness is so vast, that we can never in our own efforts, our own sincerity, our own works, or even our own repentance, ever please God sufficiently to warrant forgiveness of sins. Something more is needed than man's efforts.
This is why in Christianity God provides for us the very forgiveness that our sincerity and repentance cannot bring. If our salvation, our forgiveness of sins, could come by anything that we do, then Jesus did not need to die on the cross (Gal. 2:21). But, it was necessary that Jesus, who was God in flesh, second person of the Trinity, provide for us what we could not accomplish ourselves. Only in Christianity is the infinite love of God manifested so completely that he humbles himself and loves us so much that he took our place of punishment to ensure salvation. This is good news for the Christian. But, the Muslim has no such good news. He is stuck with the uncertain hope that maybe, just maybe his own sincerity and repentance are good enough to warrant forgiveness from his God.
Again, in contrast, the God of Islam accepts the sin-touched sincerity and sin-touched repentance of Muslims. This is a demonstration that the God of Islam, because it was invented by Mohammed, is inferior to the Christian concept of the infinite holiness of God. Therefore, we conclude that the God of Islam is not holy because it accepts the sin-touched repentance and sin-touched sincerity of Muslims for forgiveness of their sins. By contrast, the God of Christianity does not accept them because He is too holy to accept people's sin-touched efforts. The God of Christianity is too holy for that. But, the God of Islam is not. The God of Christianity provides what sinful man cannot: the cleansing of our sins by HIS work (on the cross), not sinful man's sincerity or sinful man's repentance. The God of Islam requires that man's efforts be good enough to "hopefully" gain salvation. To which system do you wish to place your hopes, in Christianity where God provides and guarantees salvation or in Islam where Allah does not?