In the fifth century, Peter the Fuller, patriarch of Antioch, added the clause who was crucified for us to the Trisagion as customarily sung in his see, a change that ignited one of the more consequential liturgical controversies of the period because of what it seemed to imply theologically: opponents read the addition as asserting that the Trinity as a whole, rather than Christ specifically in his human nature, had suffered crucifixion, a position associated with the theological error called theopaschism. Defenders of the addition argued it was addressed to Christ alone within the Trisagion's threefold praise and carried no such implication, but the dispute became entangled with the wider fifth and sixth century controversies over Chalcedonian Christology, and communities that retained Peter's addition became identified, rightly or wrongly, with anti Chalcedonian theological positions.
The unmodified, older form of the Trisagion, without the added clause, remained and remains standard in Byzantine Chalcedonian Orthodox and Eastern Catholic liturgy, sung in the elaborate multi part choral settings characteristic of Byzantine chant near the start of the Divine Liturgy, while the added clause survives today specifically within the Oriental Orthodox churches, including the Coptic, Syriac and Armenian traditions, whose continued use of Peter's addition several centuries later remains one of the clearest living liturgical markers distinguishing Oriental Orthodox practice from Eastern Orthodox Chalcedonian practice on a single, specific point of wording.