From Bl. Mary of Agreda's Mystical City of God:
CHAPTER XXIX.
CHRIST RETURNS WITH THE FIVE FIRST DISCIPLES TO NAZARETH; HE BAPTIZES HIS MOST HOLY MOTHER; OTHER INCIDENTS DURING THIS TIME.
319. The most blessed Lady also asked Him for the Sacrament of Baptism, which He had now instituted, and which He had promised Her before. In order that this might be administered with a dignity becoming as well the Son as the Mother, an innumerable host of angelic spirits descended from heaven in visible
forms. Attended by them, Christ himself baptized his purest Mother.
Immediately the voice of the eternal Father was heard saying: "This is my beloved Daughter, in whom I take delight". The incarnate Word said: "This is my Mother, much beloved, whom I have chosen and who will assist Me in all my works." And the Holy Ghost added: "This is my Spouse, chosen among thousands." The purest Lady felt and received such great and numerous effects of grace in her soul, that no human words can describe them; for She was exalted to new heights of grace and her holy soul was made resplendent with new and exquisite beauty of heaven. She received the characteristic token impressed by this Sacrament, namely, that of the children of Christ in his holy Church. In addition to the ordinary effects of this Sacrament (outside of the remission of sins, of which She stood in no need), She merited especial graces................