"After witnessing Suleiman reach Vienna in 1529, both Luther and Calvin came to fear the influence of Islam and denigrated Muhammad as a consequence of that fear. Calvin in particular condemned Islam for its veneration of Muhammad as a prophet and claimed that Muslims set Mohammed apart from other men as an idol. In his Institutes of the Christian Religion (1536), Calvin condemns the treatment of Muhammad as that of an idol. “The Turks in the present day”, he states, proclaim “with full throat that the Creator of heaven and earth is their God”, yet they reject the sovereignty of Christ and “substitute an idol in His place”. The replacing of Jesus with Muhammad is a grievous action for Calvin. He proclaims in a sermon, “[the Turks] set their Mahomet in the place of God’s Son”, for which he questions, “ought such a one be put to death, without forbearing?”"