The Trisagion recalls the threefold cry of “Holy, holy, holy” by the angels before the throne of God in the vision of Isaiah. It marks the Church's deep reverence before the infinite holiness of God as it approaches the holy Sacrifice. In the Syrian Church, the Trisagion is addressed not to the Holy Trinity but to Christ, the Son, which explains the addition of the words “who were crucified for us” at the end.