O God, who by the Immaculate Conception of the Blessed Virgin Mary, didst prepare a worthy dwelling place for thy Son, we beseech thee that, as by the foreseen death of this, thy Son, thou didst preserve her from all stain, so too thou wouldst permit us, purified through her intercession, to come unto thee. Through the same Lord Jesus Christ, thy Son, who livest and reignest with thee in the unity of the Holy Ghost, God, world without end. Amen.
Further reading
The prayer gives thanks for the grace with which God prepared Mary to become the mother of his Son. Scott Hahn’s Hail, Holy Queen explores the biblical foundations of Catholic teaching about Mary, including her Immaculate Conception, for readers who want to understand the faith expressed in these words.
Hail, Holy Queen: The Mother of God in the Word of God by Scott Hahn (paperback) on Amazon (paid link)