“Lord Jesus Christ our God, uncircumscribed in your divine nature, having become inexpressibly incarnate for the salvation of man ultimately by the Virgin Mother of God, Mary, has become worthy of circumscription. Who, having imprinted the sacred features of Thy immaculate face on the Holy Veil, and through healing the illness of the governor Abgar and bringing about the enlightenment of his soul into the full knowledge of our true God and who, through thy Holy spirit brought wisdom to the holy apostle and evangelist Luke to depict the form of thy most innocent Mother, who carried Thee in her arms as a child and said ”May the grace of Him who was born of me, through me be imparted to them”, the same, o God and master of all things, enlighten and bring wisdom to the souland heart and mind of thy servant {name } and direct these hands for the irreproachable and excellent depiction of the form of thy person and of Thy immaculate Mother and of all thy saints, to the glory and to the splendour and beautification of Thy holy Church, and the remission of the sins of those worshiping in regard to the church and devoutly kissing and so referring honour to the prototype, redeem him from all harm inflicted by the devil, as he diligently follows all the commands of the ministers of thy immaculate mother, of the holy and illustrious apostle and evangelist, Luke, and of all the saints. Amen”.
From “The painters manual of Dionysios of Fourna”