E.-Syr. abbot and bp., the author of a monastic history. Toma son of Yaʿqob, was born in the 810s in the village of Neḥshon (Book of Governors, II, 311) in the district of Beth Sharonaye, in the diocese of Slokh, Adiabene.

In 832, as a ‘young man’ he became a monk in the Monastery of Beth ʿAbe (‘The Forest Monastery’), in Marga, ca 100 km. north-east of Mosul. It was one of the most renowned E.-Syr. monasteries, from which many bps., metropolitans, and catholicoi of the E.-Syr. Church hailed. When in the year 837 a former monk and abbot of Beth ʿAbe, Abraham, became Cath. (Abraham  II, 837–50), Toma, his friend in the monastery, became his secretary. A few years later (in 840s) Abraham appointed Toma bp. of Marga. We know nothing more about his life, and even the date of his death remains unknown.

For a long time it was thought that Toma was also appointed by Cath. Abraham II metropolitan of Beth Garmai, and that he was a brother of Cath. Theodosios (853–58). However, in the light of Fiey’s research (1965, 362–4), it appears that Toma of Marga and Toma the metropolitan of Beth Garmai are two different persons.

Toma wrote three books, all within the genre of monastic history.

The first of them, which may have been entitled ‘The Histories of certain holy men’, is only known from his own mention of it in the ‘Book of Governors’. It is probable that the material of the former book was re-used by Toma in the latter.

Toma’s second work was ‘The History of the Monastery of Rabban Cyprian’ (in Birtha, in the diocese of Marga), which contained an account of the first monks (before Abraham of Kashkar) in this region. This, although written earlier, was incorporated as the 6th book of Toma’s third and most comprehensive work:

The Book of the Governors (Syr. ktābā d-rešāne), scil. of the Monastery of Beth ʿAbe (better: Book of Abbots), is also known in Western scholarship as Historia Monastica. This short title is known only from the colophon, whereas the full Syriac title is: ‘Useful stories and accounts of holy men and monks who for generations lived in the holy monastery of Beth ʿAbe, written by the venerable Mar Toma bishop of Marga’. The work was most probably written ca. 850 when Toma already was the bp. of Marga. He dedicated it to ʿAbdishoʿ, another monk in the same monastery, who encouraged him to write. It was modelled on the pattern of the Paradise of Palladius, known to Toma in the redaction of ʿEnanishoʿ (ca. 670) (Budge, The Book, vol. 1, xxxi–xxxiii). It provides not only a series of lives of the abbots, but also information on the catholicoi, metropolitans, and bps., as well as on the establishment of schools, theological controversies, etc. There is much material both on monks from other monastic houses (those on Mount Izla) and on the development of E.-Syr. monasticism in general from the 6th until the 9th cent. Toma also provides important accounts of the non-monastic history of the Ch. of E., such as the conversion of the peoples living southeast of the Caspian Sea and the missions to South Arabia, Persia, and China. He writes on the relations of the Christians with the Persian and later Muslim authorities, but also on matters such as the murder of the Sasanian king Khusrau and the expansion of the Muslim empire.

Toma has also shown his poetical skills by inserting into Book 3 a memrā in the 12–syllable meter on Maranʿammeh, metropolitan of Arbela, i.e., of Adiabene, who had also been a monk of Beth ʿAbe.