Principi Apostolorum Petro §19

¹⁹ Regarding his devotion to the Virgin Mother of God, who can say enough? "You, O Lord and your Mother" he says in a Nisibean poem, "are the only ones who are in all respects perfect beauty; in you, my Lord, there is no stain, nor in your Mother is there any dishonor." "The lyre of the Holy Spirit" never sounded sweeter than when he was asked to sing the praises of Mary or to celebrate her perfect virginity, her divine maternity, or her full patronage of mercy toward man.