Veg Saying of Jesus from Islam
Christ said, “Flesh eating flesh? How offensive an act!” - The Muslim Jesus: Sayings and Stories in Islamic Literature, by Tarif Khalidi:
https://archive.org/details/muslimjesussayin0000khal
The saying above reminds me of The Gospel of Thomas, Saying 112: Soul should be independent of flesh: Jesus said, “Woe to the flesh that depends upon a soul. Woe to the soul that depends upon flesh.” (The Gnostic Scriptures, Bentley Layton, David Brakke)
Because some Ebionite Christians held out longer in Arabia, that's probably why some in Islam had an awareness about Christian veg teachings.