Council of Constantinople 1156
The Life-giving sacrifice has never been offered only to the Father of the Only Begotten Who is the Source of all things, neither when it was first offered by Christ the Saviour, nor at any subsequent time even to the present day. It has always been offered also to the Word, Who became incarnate; and the Holy Spirit is not left out of so divine an honour. The oblation of the Mysteries which is consecrated on each occasion by the power of the Trinity, has been made (and is still made) to the Godhead over all, in the Trinity of Hypostases, which is known to us as united and as one in the same nature, and as co-eternal. (PG 115.140-8.)
