You should understand that Jews and Muslims deny that Jesus is the promised Messiah that died for our sins. Pray for their salvation, but do not listen to or encourage their false teaching
After thinking about Rev. 7:9 for a while, Perhaps it is time that I read the Letter again. Perhaps Isaiah also to get a clearer picture? I have probably mentioned that I tried to be Muslim for a decade but true knowledge of God and Jesus would not cease. I am not going into the whole story, but I have good reason to doubt the Christians, and wonder where some Muslims get their ideas about violence? "There are none righteous, no not one."