Roman Catholicism teaches in its Catechism that Muslims worship the same God Christians do and are included in the plan of salvation:
“The plan of salvation also includes those who acknowledge the Creator, in the first place amongst whom are the Muslims; these profess to hold the faith of Abraham, and together with us they adore the one, merciful God, mankind’s judge on the last day” (841).
If there is any confusion about the meaning of the Catechism, the document Nostra aetate from Vatican II clears it up:
“The Church regards with esteem also the Moslems. They adore the one God, living and subsisting in Himself; merciful and all-powerful, the Creator of heaven and earth, who has spoken to men; they take pains to submit wholeheartedly to even His inscrutable decrees, just as Abraham, with whom the faith of Islam takes pleasure in linking itself, submitted to God. . . . Finally, they value the moral life and worship God especially through prayer, almsgiving and fasting.”
When it comes to the question of whether Muslims worship the same God we do, the answer must be a resounding no. Muslims deny the crucifixion of Christ, the resurrection of Christ, the pre-existence of Christ, the sonship of Christ, the deity of Christ, the deity of the Holy Spirit, that God is Father, the Trinity, and have a long history of persecuting Christians. No one can worship the one true God who does not honor the Son in the same way he honors the Father:
“That all may honor the Son, just as they honor the Father. Whoever does not honor the Son does not honor the Father who sent him” (John 5:23).
Do Muslims honor the Son just as they honor the Father? They cannot by definition because they deny that the Son is God and they deny that God is Father. Because they do not honor the Son as God, they do not honor the Father. Because they do not honor the Father, they do not worship him. Can one honor God by dishonoring his Son? Is God honored by worship that denies who he is?
No one can worship God who is not saved. Worship is something that is pleasing to God and only those who are in the Spirit can do anything pleasing to him (Rom 8:8-9). But only those who are saved have the indwelling Holy Spirit. Muslims are not saved because they deny the deity of Christ and his death and resurrection (Rom 10:9).
The book of 1 John answers this question directly:
“No one who denies the Son has the Father. Whoever confesses the Son has the Father also. Let what you heard from the beginning abide in you. If what you heard from the beginning abides in you, then you too will abide in the Son and in the Father” (1 John 2:23-24).
Muslims deny the heart of the gospel: that Jesus is God, that he died on the cross for sinners, and that he was raised from the dead. Because Muslims deny the Son, they do not have the Father. How can they worship God when they deny the Father and the Son?
Because Muslims deny that Jesus is the Son of God, they do not have salvation: “Who is it that overcomes the world except the one who believes that Jesus is the Son of God?” (1 John 5:5). Muslims do not abide in the teachings of Christ and therefore do not have God: “Everyone who goes on ahead and does not abide in the teaching of Christ, does not have God. Whoever abides in the teaching has both the Father and the Son” (2 John 1:9).
False religions like Islam are a rejection of the gospel because they reject that Jesus is God’s Son. The Jesus of Islam is “another Jesus” about which Paul warned us (2 Cor 11:4). Muslims may claim that they worship the God of Abraham, but we know that the God of Abraham is not unitarian in person, but exists eternally as the Father, the Son, and the Holy Spirit. God can only be worshiped in truth and therefore those who do not worship him according to his Word do not worship him at all. As John 4:24 says, “God is spirit, and those who worship him must worship in spirit and truth.”