What to know One of the distinctions followers of Jesus often make between al-Masih (the Messiah) and Mohammad is about the topic of women: how God said they should be treated, and how Jesus and Mohammad themselves behaved towards them. Your friend may recognize the polygamy of Ibrahim (including his sexual relationship with a slave woman) as aligned with the Qur'an, rather than the Injeel. This is a significant topic. Although this is a Bible study guide, and not a resource for polemics against Islam, we need to pause to ensure that you have a baseline of accuracy about Islamic marriage and sexuality laws. For brevity, we'll include only one source per statement.
Mohammad took a six year old girl (Aisha) as his wife, consummating the marriage at age nine. (Sahih al-Bukhari, 7:62:64)
Mohammad said that the message of Allah announces that slaves and war-captives can be used for sex by their captors. (Qur'an 4:24)
Some of Mohammad's first followers resisted his that they could have sex with war captives (whose husbands were alive). Mohammad's response: "Verily, you do it, you do it, you do it." (Sunan Abu-Dawud 5:2150)
Note that Islam's sources also record the physical and sexual actions of Mohammad towards young boys.
To followers of Jesus, then, the example of Ibrahim in this passage, and the apparent silence of God about both polygamy and sexual acts with a slave, can be deeply troubling. (In regards to female survivors of war...Deuteronomy 21:10-14 is surprising and troubling as well.) Our Muslim friends might point this out: Ibrahim aligned with Islam, not Christianity. How can we respond? What to say
Begin with Mark 10. Jesus is clear in giving a definition and standard of marriage (and male/ female sexual relationships) that's much more restrictive and narrow than any prophet before him. In this same passage, He's asked how he can "go against" the law of Musa (Moses). Jesus responds by saying this is the true standard of God, evident since the creation of man and woman. He also goes on to explain why God allowed a lower standard to exist before the days of al-Masih.
Move forward to Matthew 5 (emphasis on 17-48). Again in this passage, Jesus elevated the standard of God, while teaching that He wasn't abolishing or erasing God's Word...He was fulfilling it. Notice that in this passage, He gave His words the same authority as what was reserved for from God himself. That is: in addition to receiving messages from God, Musa received tablets inscribed by God Himself. After Musa, prophets always spoke the "Word of the Lord" that came to them. But Jesus didn't receive an inscription on a stone, or proclaim that a message had come to Him: He Himself was the Word. Jesus Himself had authority to speak Scripture ("You have heard it said...But I say...") Pause to recognize the implications of this.
Read Matthew 9, with an emphasis on verses 16-17. In this passage, we see Jesus describe the nature of His words and message as something that is fundamentally different from what preceded it: so different, that it would be foolish and misguided to try to force-fit it to what came before. His message - while fulfilling previous prophecy, law, and teaching - would be revealed as radically different from what mankind had imagined (1 Corinthians 2:8-10)...although both the prophets and the angels looked attentively towards this awesome wonder (1 Peter 10-12).
This isn't abrogation (the Islamic concept that the new prophetic message replaces the old)...this is a New Covenant: a new relationship made possible between God and man, because of the crucifixion and resurrection of Jesus al-Masih. Invite your friend to explore this topic further by reading the book of John or Matthew together, or use the storyset "Al-Masih."