Adam, Abraham, Moses all these people taught that the wages of sin is death.?

Mohammed substitutes death with sincere repentance. Throughout Jewish history, lambs were killed as a sacrifice for remission of sin and without the shedding of blood there was no remission. If Allah is the same God Abraham worshiped, does this mean he softened and now accepts substitutes? Can man sincerely repent? Am very afraid for Mohammedans.