The relationship between God and Man: In the Islamic faith God does not reveal himself at all. He remains at a distance. The constant call "Allahu Akbar" manifests: One cannot enter into a relationship with Allah he always remains in the other world, like an oriental ruler enthroned high above his subjects.
Father - Child relationship: For a Muslim, the concept of men being God's children and God being a Father (Abba dear father Romans 8:15), are not only incomprehensible but blasphemous, since Allah lives strictly apart from this world.
God as man: the crucial event in the Bible's salvation account is God becoming man in Jesus Christ. God not only walked among us, He suffered for the sins of the world on the cross. The resultant salvation of man is inconceivable to the Muslim.
God's mercy and love: God is merciful to the sinner and the price paid for his mercy is unbelievably high: "you have burdened me with your sins and wearied me with your offences (Is 43:24) God is merciful to us because of our salvation costs him dearly (1 Corinthians 6:20, 1 Peter 19). The mercy of Allah cost him nothing.
God is our confidence: The Islamic faith cannot conceive of a God who gives us peace and assurance of salvation: "For I am convinced that neither death or life... will be able to separate us from the love of God that is in Jesus Christ our Lord" (Romans 8:38-39). The Islamic faith cannot conceive of a God humbling himself on the cross and the Holy Spirit being poured out in our hearts. It cannot imagine Jesus' coming in glory.
The God of the Qur'an and the God of the Bible may show verbal similarities
here and there. But on closer inspection they do not have much in common.
Therefore it is not the same God to whom Christians and Muslims pray.