My Jesus, I firmly believe that Thou art present — Body, Blood, Soul and Divinity — in the Blessed Sacrament of the altar. Lord, I believe, help my unbelief. Lord, increase my faith. [pause] I love Thee above all things and desire Thee in my soul. Yet my love is weak and inconstant, strengthen my love evermore. [pause] Since I cannot now receive Thee under the sacramental veil, I beseech Thee, with a heart full of love and longing, to come spiritually into my soul. [pause] As though Thou wert already there, I embrace Thee and unite myself wholly to Thee; permit not that I should ever be separated from Thee: Thou in me and I in Thee, in time and in eternity, in Mary — in Her Immaculate Heart. Amen.
A spiritual communion can be offered any time during the day. A person can also make numerous such acts throughout the day. The grace which one receives though this act is dependent upon the sate of one's soul, as well as one's fervor, purity of heart and sanctity.
There is no one single prayer by which one can offer a spiritual communion. Many variations exist. This one is based on a popular prayer by St. Alphonsus Liguori and augmented by Fr. Rodríguez with passages from Scripture and insights from St. John Eudes and St. Louis de Montfort.