Al-Jawab al-Sahih Liman Baddala Din al-Masih is a work authored by Shaykh al-Islam Ibn Taymiyyah in refutation of a treatise originating from Qubrus by a Christian monk called Paul of Antioch who attempted to argue for Christianity by both reason and revelation (i.e. using the Qur'an itself) and dismissing that the call of Islam is applicable to them, the Christians. Ibn Taymiyyah also intended this work as a general invitation to Christians to Islam, beyond the specific purpose for which it was mainly written.
Download Part 1. The universal nature of Muhammad's prophethood and explanation of the reason for the writing of the treatise and indication that the manner of straying of the innovators from Islam is similar to the manner of straying of the Christians from the deen of the Messiah, Jesus, son of Mary.