In 749 AD, just 117 years after Muhammad’s death, Doctor of the...

This was before the books of hadith were even written‼️
St. John lived under the Umayyad Caliphate. He was a highly educated man. He knew Muslims. And he called Islam "the heresy of the Ishmaelites" and "a forerunner of the Antichrist".
Sacred Scripture 📖 tells us:
🗣️"Who is the LIAR but he who denies that Jesus is the Christ? This is the ANTICHRIST, he who denies the Father and the Son." (1 John 2:22)
And indeed, Islam denies BOTH the Father AND the SON. Thus, the label is fitting.
St. John of Damascus, hero of counter-dawah, pray for us! 🙏
