" Muslims cannot know the assurance of salvation, for in the end, Allah does with each person as he desires. According to the Hadith, Muhammad himself said he was unsure of his eternal salvation. He wrote, “Though I am an Apostle of Allah, yet I do not know what Allah will do to me!” (Bukhari 5.58.266). And the Quran states that only death by jihad assures a person of instant access into paradise. Christians, however, can know the assurance of their salvation. That’s because salvation is a free gift made available through the sacrifice and triumph of Jesus. No matter how great our sin, Jesus’ sacrifice on our behalf was greater. Because it is Christ who obtained our salvation and gives it to us, we cannot and will not lose it. As the apostle John said, “Whoever has the Son has life; whoever does not have the Son of God does not have life. I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life” (1 John 5:12-13). This free gift is available to anyone who receives Christ as Savior: “To all who did receive him, to those who believed in his name, he gave the right to become children of God” (John 1:12). "

― Erwin W. Lutzer , The Cross in the Shadow of the Crescent: An Informed Response to Islam’s War with Christianity