An Orthodox Christian of Arab ethnicity (he seems to be the only saint depicted wearing a kaffiyeh or turban), John (ca 676-749) was the scion of a family of tax-collectors who successively served both the Byzantine empire and the Islamic caliphate. He followed the family profession for a time but eventually entered the monastery of St Sabas near Jerusalem, where he devoted the rest of his life to asceticism and the writing of theological treatises.

John was ordained to the priesthood in 726, the same year that the emperor Leo the Isaurian promulgated a decree against the use of icons, thus inaugurating the iconoclastic controversy. John responded to this with a vigorous defense of icons, On Holy Images. He laid the groundwork for the Eastern Church's current theology of icons, which carefully distinguishes between latreia (worship), which is due to God alone, and proskynesis (veneration) which may legitimately be rendered to the saints and their images. He was able to do this in part because he did not live in the Byzantine empire but in a Muslim-controlled polity. In another of his works he is very critical of Islam. Go figure.

I include a couple of prayers to John from the Orthodox and Anglican traditions (his feast is today and is also observed by Roman Catholics) as well as a quote from his work on icons. The latter is, I think, an appropriate corrective to certain trendy neo-Gnostic tendencies (Gnostic-Lite would probably be a better description) which one runs into sometimes in liberal mainline Protestant circles.

Kontakion tone 4

Let us sing praises to John, worthy of great honor,
the composer of hymns, the star and teacher of the Church, the defender of her doctrines.
Through the might of the Lord's Cross he overcame heretical error,
and as a fervent intercessor before God
he entreats that forgiveness of sins may be granted to all.

From Lesser Feasts and Fasts

Confirm our minds, O Lord, in the mysteries of the true faith, set forth with power by your servant John of Damascus; that we, with him, confessing Jesus to be true God and true Man, and singing the praises of the risen Lord, may, by the power of the resurrection, attain to eternal joy; through Jesus Christ our Lord, who lives and reigns with you and the Holy spirit, one God, now and for ever. Amen.

From On Holy Images

I honor all matter...and venerate it....Was not..the thrice-blessed wood of the Cross matter? Was not the sacred and holy mountain of Calvary matter? What of the life-giving rock, the Holy Sepulcher, the source of our resurrection; was it not matter? Is not the most holy book of the Gospels matter? Is not the blessed table matter which gives us the Bread of Life? Are not the gold and silver matter, out of which crosses and altar-plate and chalices made? And before all these things, is not the body and blood of our Lord matter? Either do away with the veneration...of all these things, or submit to the tradition of the Church in the veneration of images, honoring God and His friends, and following in this the grace of the Holy Spirit.