I have read a comparison between the doctrine of Islam and Christianity and it states that Mohammad and the Arabs are descendants of Ishmael, which Islam claims Jesus said by their interpretation of Matthew 21:42-44, would supersede the Israelite nation.
What is the true story behind Mat. 21:42-44?
This is a classic example of taking a passage out of context and making it say what you want it to.
In Matt. 21:42-44 the Lord was talking about the church. The Kingdom He referred to is not the Nation of Israel but the Kingdom of God, the Kingdom Jesus said was not of this world (John 18:36). After the Jews rejected their Messiah, Peter and Paul and others were told to turn to the Gentiles. Although the first Christians were of Jewish background, by the 2nd Century AD the Church was predominantly Gentile in its membership.
Jesus is the stone the builders rejected (Psalm 118:22-23). We are the people who have fallen on His Grace and produce its fruit (Gal. 5:22) not Islam.