Here’s a brief summary of Islamic beliefs with specific attention to how they related to Christianity to help you understand the points of similarity and difference between the two religions. The references in the parentheses are passages in the Qu’ran.
Muslims believe that there is one God, Allah (the word for God in Arabic), who is merciful (16:18). Oneness and mercy are the two distinguishing attributes of him. Allah created man good and uncorrupted, but not in his own image (42:11) because he is too completely transcendent to share any attributes with his creatures. Creation serves as a proof of his existence (2:164, 3:190). Through the prophets Noah, Abraham (3:67), Ishmael, Isaac, Jacob, Moses, David and John among others (4:163), he gives a law to submit to, but we forget to follow it. Islam accepts that the Torah (tawrat) was revealed through Moses (3:93, 6:154) and provides guidance (6:91), that the Psalms (zabur) were given through David (4:163, 17:55, 21:105) and that the Gospel (injil) revealed by Jesus. They argue that these documents were corrupted by the Jews.
Muslim scripture, the Qur’an, was written by Mohammad in Arabic through supposed direct revelation (dictation) from God. They consider the book to be a miracle because of its unmatched Arabic literary quality. Mohammad was born in 570 AD, died in 632 and received his first revelation in 610. He moved to Medina in a journey known as the hijrah in 622 and this year marks the beginning of the Muslim calendar. He is believe to be the last prophet of Allah (33:40) and brought the Qur’an to all people (2:176, 5:19). The Qur’an is a collection of revelations from God to Mohammed and consists of 114 surahs (chapters) from longest to shortest (rather than in chronological order). The first surah (al-Fatiha) is a summary of Islam and consider the greatest. The Qur’an confirms confirms (yusaddiqu) (2:91, 3:3, 81; 4:47) and explains (yufassilu) the Torah and Gospel (6:114, 10:37; 12:111), but supersedes (muhaymin) them (5:48). The Qur’an is only Allah’s word in Arabic (12:2, 20:113, 39:28, 41:2-3, 42:7), but is seen as the message to all nations (21:107, 38:87, 68:52, 81:27). Muslims are witnesses of the truth of God to the world (2:143, 22:78). There is also a second set of scriptures that they use to drive their beliefs called the Hadith. The Hadith is narrative teaching and practice of Mohammad compiled by his followers. Many Muslim laws are derived from following the pattern of Mohammed’s life rather than from the Qur’an itself.
The law is central to Islam and everyone is to submit to Allah’s rule. The word Islam itself means submission. Muslims hold that Allah is merciful and forgives us if we repent (4:110, 5:39), believe in him and do good works. The good works of prayer, fasting, alms giving (zakat), and pilgrimage (hajj), (4:122; 5:9, 93) form four of the five pillars of the religion with the declaration of faith (shahada) being the fifth. People are directly accountable their own actions and no one, such as Jesus, can intercede in our place as a mediator (1:48, 123; 17:15). People can make up for bad deeds with good ones (11:114). Allah’s nature allows him to forgive sins directly without punishment or justice for breaking his law and he has mercy on whom he wills (2:284, 3:74, 135, 193; 5:41). The atonement provided by the cross is therefore unnecessary.
Jesus is held in highest regard in Islam, and is second only to Mohammad, yet was merely a special prophet/messenger (4:171, 5:74) among many prophets who proclaimed Allah’s law throughout history. Though they believe that Jesus was born of the virgin Mary (3:39, 47) and lived a sinless life, they do not believe that He is not the Son of God because Allah cannot have children (3:62, 4:171), nor can God take on human flesh because he would never lower himself in that manner. Jesus was created with the same nature as Adam (3:59) and isn’t eternal (3:59). He slept and needed to eat, neither of which would be needed of God. Allah is one being and does not have ‘partners’ (5:72-73), so the idea of ascribing the Son and Spirit (or Mary as some Muslims think Christians believe) as ‘partners’ to God (the Trinity) is the highest heresy (4:48, 115-116; 5:72-73). They think Jesus’ Gospel message (5:46) was about submission to Allah and was consistent with what the previous prophets taught. His message was proclaimed to Israel only (3:48-57), but the disciples corrupted it. Jesus didn’t die on a cross (4:157); instead someone who looked like Jesus was crucified in his place. He ascended to heaven without dying (4:158). They expect him to return to judge those who made Him a partner with God (4:159).
People will receive their due wages on the Day of Resurrection (3:185). Paradise is the reward for those who do righteous deeds (sawab, 3:136, 198; 4:57). Hell (a torment of fire) is the destiny of those who don’t believe (3:191, 4:14) or obtain enough sawab. Muslims have no assurance of whether they’ll go to heaven or hell after they die.
If you’d like to learn more, listen to this 15 minute Islam 101 discussion from Desiring God or read The Prophet and the Messiah by Chawkat Moucarty, which much of this post is based on. For the best doctrine-by-doctrine comparison of Islam and Christianity see Rick Brown’s article Muslim Worldview and the Bible. Additional helpful articles can be found in the International Journal of Frontier Missions.