I like that hymn.
"This Virgin Mother of the Only-begotten of God, is called Mary, worthy of God, immaculate of the immaculate, one of the one."
Origen,Homily 1(A.D. 244),in ULL,94
"Thou alone and thy Mother are in all things fair, there is no flaw in thee and no stain in thy Mother."
"Ephraem,Nisibene Hymns,27:8(A.D. 370),in THEO,132
"Mary, a Virgin not only undefiled but a Virgin whom grace has made inviolate, free of every stain of sin."
Ambrose,Sermon 22:30(A.D. 388),in JUR,II:166
"We must except the Holy Virgin Mary, concerning whom I wish to raise no question when it touches the subject of sins, out of honour to the Lord; for from Him we know what abundance of grace for overcoming sin in every particular was conferred upon her who had the merit to conceive and bear Him who undoubtedly had no sin."
Augustine,Nature and Grace,42(A.D.415),in NPNF1,V:135
"As he formed her without my stain of her own,so He proceeded from her contracting no stain."
Proclus of Constantinople,Homily 1(ante A.D. 446),in ULL,97
"A virgin, innocent, spotless, free of all defect, untouched, unsullied, holy in soul and body, like a lily sprouting among thorns."
Theodotus of Ancrya,Homily VI:11(ante A.D. 446),in THEO,339
"The angel took not the Virgin from Joseph, but gave her to Christ, to whom she was pledged from Joseph, but gave her to Christ, to whom she was pledged in the womb, when she was made."
Peter Chrysologus,Sermon 140(A.D. 449),in ULL,97
"[T]he very fact that God has elected her proves that none was ever holier than Mary, if any stain had disfigured her soul, if any other virgin had been purer and holier, God would have selected her and rejected Mary."
Jacob of Sarug(ante A.D. 521),in CE