The ritual of the Asperges, or sprinkling with holy water, uses words from Psalm 51, and is traditionally conducted before the start of a Tridentine Mass, before the Prayers before Mass. It may also be used more extensively when it is necessary for anything to be asperged, that is, sprinkled with holy water.

Asperges me, Domine, hyssopo, et mundabor: lavabis me, et super nivem dealbabor.
Miserere mei, Deus, secundum magnam misericirdiam tuam.
Gloria Patri, et Filio, et Spiritu Sancti
Sicut erat in principio, et nunc, et semper, et in saecula saeculorum. Amen.
Antiphon: Asperges me, Domine, hyssopo, et mundabor: lavabis me, et super nivem dealbabor.

Thou shalt sprinkle me, O Lord, with hyssop, and I shall be cleansed: Thou shalt wash me, and I shall be made whiter than snow.
Have mercy on me, O God, according to Thy great mercy.
Glory be to the Father, and to the Son, and to the Holy Ghost
As it was in the beginning, now and always, and in the ages of ages. Amen.
Antiphon: Thou shalt sprinkle me, O Lord, with hyssop, and I shall be cleansed: Thou shalt wash me, and I shall be made whiter than snow.

Followed by:
Whitmonday to Holy Saturday: Exaudi nos, Domine sancte
Easter Sunday to Whitsunday: Vidi aquam