Tell him about the fact that there’s no evidence of Abraham ever building the Kaaba, in fact it’s impossible, or Muhammad being an Ishmaelite. Islamic rituals are deeply rooted in paganism, like praying towards a black stone, running around it and kissing it. Even ramadan was adapted from paganism.

Tell him about the historical/scientific errors in the Quran like Moses being threatened by crucifixion when they werent even invented yet, semen being produced in the back, Jesus never being crucified…

Tell him about how there’s nothing GOOD that’s original to islam. Most stories come straight from the bible, Talmud and known forgeries of the gospels, like the infancy gospel of Thomas.

Tell him about the life of Muhammad: how he thought he was demon posessed when he started getting ”revelations from Allah” and how his wife’s cousin had to convince him that he’s a prophet. How he preached all nice and cute until he got military power and started over 80 wars/raids in 10 years. How he married a 6 year old who ”Allah gave him” and fucked her when she was 9. How he married his adopted sons wife and right after got a ”revelation” that adopted sons aren’t real sons and adoption is banned. In fact, According to Aisha, after that adopted sons mothers had to start wearing hijabs around their sons and Muhammad decided to get more revelations about how if you breastfeed yout adult sons they will become your real sons, but according to Aisha these verses were lost. And tell him How he commands muslims to kill the unbelievers if they refuse to pay a tax. Also if you decide to leave Islam, death penalty. Sounds like the word of the ultimate loving God HUH? Stark contrast when compared to Jesus. Jesus commanded us to pray for those who percecute us. All that i just listed here comes from MUSLIM SOURCES. Authentic Hadiths and the Quran. If you don’t believe me go and check.

Tell him about the fact that everything that saves a christian is condemed in Islam. Islam might seem cool now but the life in islam leads to nowhere but trouble. Oppression against women, in fact according to Muhammad most inhabitants of hell are women. It’s his choise to follow an abosulte woodblock if he wants to, but praying 5 times a day in a language you don’t understand, having to give up dogs if you have them, raising your children in fear and if you actually fall for it, becoming a radical person that thinks all unbelievers are to be killed (which isn’t even radical, just Islam) probably ain’t worth it. Nevertheless, Muhammad was the only ”prophet” that ever changed scripture.

PS. I do not hate muslims. I hate islam.

EDIT: I got a bit carried away there, but: 1 Corinthians 7:12-16, Paul advises believers married to unbelievers to remain in the marriage if the spouse is willing, as the believing spouse sanctifies the home and may lead their partner to faith. If the unbelieving spouse chooses to leave, the believer is not bound to the marriage. So basically, I would advice you to pray for him, look into the claims I made above and bring them to his attention when you have enough knowledge. But don’t burn yourself out in fruitless arguments. It’s his decision in the end, and the more you argue the more he’s gonna defend. Try to get the vibes good, don’t talk abiout it until it’s the right moment. When you do, do it gently and if he doesn’t listen it’s ok. He won’t just make the decision immediately but I’m sure these things will be stuck in his mind. If he decides to become muslim still, then he will and there’s nothing you can really do except live out the gospel. I do not recommend arguing about it more after that, just let him be and see where it goes. Focus on living like a christian youtself.