Vidi Aquam, Gregorian Chant
One of the joyful features of Paschaltide is the substitution of singing the Asperges antiphon during the rite of sprinkling holy water (just before the Sunday High Mass) with the Paschal antiphon of Vidi aquam. Dom Prosper Gueranger explains in The Liturgical Year the sentiments we should have during this significant rite of purification that precedes Mass:
During the Asperges [Vidi aquam], let us recall to our minds the Baptism received on Easter Eve by the Neophytes. Let us also think of our own, whereby we were made members of Christ. The water that thus regenerated us was made fruitful by the Blood of the Lamb and by the power of the Holy Ghost."
These holy aspirations have an even greater application during Eastertide as seen by the words of the Vidi aquam antiphon, which have a double allusion: the first to Ezekiel's vision (see verse 47 in the book of the same name) and the second to the water and blood that flowed from Christ's body when His side was pierced by a lance.
This symbolism is even furthered by the first ceremonial action of the celebrant when he sprinkles the foot of the altar, which mystically represents the body of Christ and from whose Passion, Death and Resurrection our salvation has been obtained—which the sacrificial stone continues through the supernatural life it gives to souls.
Vidi aquam egredientem de templo, a latere dextro, alleluia: et omnes, ad quos pervenit aqua ista, salvi facti sunt, et dicent, alleluia, alleluia. (Ps. 117) Confitemini Domino quoniam bonus: Quoniam in saeculum misericordia eius. Gloria Patri, et Filio, et Spiritui Sancto: Sicut erat in principio, et nunc, et semper, et in saecula sæculorum. Amen.
I saw water flowing from the right side of the temple, alleluia; and all they to whom that water came were saved, and they shall say, alleluia, alleluia. (Psalm 117) Praise the Lord, for He is good; For His mercy endureth forever. Glory be to the Father, and to the Son, and to the Holy Ghost. As it was in the beginning, is now, and ever shall be, world without end. Amen.