Thomas of Edessa
Thomas of Edessa lived in the early 6th century. He was a pupil at the Nestorian theological school at Nisibis of Mar Aba, subsequently Patriarch. He travelled to Constantinople, as he tells us himself, in order to acquire Greek learning. Thomas' death is mentioned by Cosmas Indicopleustes (II.2) as a recent event in 544 AD. Two works have survived.
A single manuscript (Ms. Seert 82, known as S) from Seert, written in the 16th century and destroyed in the sack of the Chaldaean Patriarchate in Baghdad in 1915 contains a set of 13 Expositions of the Feasts of the Economy by various authors, including Thomas of Edessa and his pupil and successor Cyrus of Edessa. A copy of this (=A) was made by the hieromonk Samuel Jamil in 1885; from this derive the other 7 copies thought to exist today. It is possible that A was destroyed in the troubles following the US occupation of Iraq, when the Chaldaean Cathedral was bombed, but this is not certainly known.
Thomas of Edessa wrote explanations of why the feasts of Christmas and Epiphany are celebrated (Nos 1 and 3 in the collection). Cyrus indicates that Thomas was commissioned to write on all 8 feasts but died before he could complete the task; Cyrus then wrote the other 6, and further texts have been added since.
The work on Christmas was edited and translated into Latin from a handwritten copy of a copy by S.J.Carr; the work on Epiphany has never been edited, but is to be found in the same manuscript copies listed by Macomber for Cyrus of Edessa.
According to Thomas (De Nat. I, p.5 line 7 of the text; p.14 of the translation), the two explanations were delivered orally by the future patriarch Mar Aba I (540-552). Thomas probably composed them between 538-543.