Injeel is the Arabic word used for the Book of Prophet Jesus. Arab Christians in pre-Islamic times used this word to refer to the NT, or new covenant given by Christ.
The Injeel is the message of God for those who follow Jesus the Christ. So you wonder that if Muslims are to believe in the Injeel, why do some Islamic governments forbid their citizens to read it?
Muslims are obligated to honour Al-Qur’an Al-Karim and all the holy books that God sent to humans — Al-Tawrat (the Book of Moses), Az-Zubar (the Book of David), and Al-Injeel (the Book of Jesus).
Muslims are told they must honour these four books, but they only follow the Holy Qur’an (Al-Qur’an Al-Karim). They follow the doctrine of tahrif, an idea that says Jews and Christians corrupted the original texts of the Tawrat and Injeel.
The best thing to tell a Muslim who believes that the Injeel is corrupted is to study it and uncover its corruption for themselves. Things are not always as they seem.