Isaías 6
Cosmas Indicopleustes
Isaías 6:3
he saw the Lord sitting on a throne high and lifted up, while the Seraphim stood in a circle around him, the one having six wings, and the other six wings, with which they did cover themselves, and the one cried out to the other and said: Holy, holy, holy Lord of Sabaoth! the whole earth is full of his glory. — The Christian Topography, Book 5
Isaías 6:3
God again used an expression ambiguously respecting the Trinity, repeating thrice through Isaiah the word Holy which he made applicable to one God, saying: The Lord of hosts, the whole earth is full of His glory; showing both the number of the three Persons and the unity of the Godhead. — The Christian Topography, Book 5