The hymn has a companion piece, "Tantum Ergo Sacramentum," which is similarly the final two stanzas of another of Aquinas's works, Pange Lingua . Together, these texts provide the spiritual and musical framework for Benediction.
"O Salutaris Hostia" is one of the most enduring expressions of Eucharistic devotion in the Catholic Church. Composed by the preeminent theologian St. Thomas Aquinas in the 13th century, it remains a cornerstone of liturgical prayer, specifically during the Exposition and Adoration of the Blessed Sacrament. O Salutaris Hostia - Catholic Latin Hymn
The middle lines ( Bella premunt hostilia ) acknowledge the "hostile battles" or spiritual struggles that believers face, asking God for the "oak-like" strength ( robur ) to persevere. The hymn has a companion piece, "Tantum Ergo