Preparation for the Gospel

At High Mass the Priest blesses the incense while the Deacon places the Book of the Gospels on the altar.  The Priest, bowing deeply, (or the Deacon kneeling) prepares himself for reading the Gospel by reciting the following prayer:

MUNDA cor meum ac labia mea, omnipotens Deus, qui labia Isaiae Prophetae calculo mundasti ignito: ita me tua grata miseratione dignare mundare, ut sanctum Evangelium tuum digne valeam nuntiare.  Per Christum Dominum nostrum.  Amen.

CLEANSE my heart and my lips, O Almighty God, Who cleansed the lips of the Prophet Isaiah with a burning coal.  In Thy gracious mercy deign so to purify me that I may worthily proclaim Thy holy Gospel.  Through Christ our Lord.  Amen.