Christianity centers on the triune God and the finished work of Jesus Christ as the only Savior, whereas Islam emphasizes the absolute unity of God (Tawhid) and rejects the divinity of Christ and the necessity of his atonement. While both are monotheistic, they differ fundamentally on the nature of God, the identity of Jesus, and the path to salvation.
Christianity teaches that the one true God subsists eternally in three distinct persons: Father, Son, and Holy Spirit (Small Catechism — Question 8). This is not a belief in three gods, but in one indivisible divine nature (Second Helvetic Confession — Ch. III). Conversely, Islam strictly asserts the doctrine of Tawhid, which denies any plurality of persons within the Godhead, viewing the Christian understanding of the Trinity as a compromise of God’s oneness.
The heart of the Christian faith is that Jesus Christ is the eternal Son of God made flesh, the only Mediator between God and man (Second Helvetic Confession — Ch. XI). Scripture declares he died for our sins and rose again, offering full pardon to all who believe. Islam honors Jesus (Isa) as a prophet, but it explicitly rejects his divine sonship and denies that he was crucified for the atonement of sins, viewing such claims as blasphemy (Small Catechism — Question 10).
Christianity maintains that we are righteous before God only by grace, through faith in the finished work of Jesus Christ (Heidelberg Catechism — Q. 60). We are more sinful than we ever dared believe and more loved in Christ than we ever dared hope. In contrast, Islamic tradition teaches a path of submission and obedience to the law and revelations of God, where salvation is generally understood in terms of merit and God’s mercy toward those who perform good works.