ABBONDIO, saint. — Fourth bishop of Como, patron of the diocese. He is particularly known for the mission he carried out in Constantinople in 450, as legate of Leo the Great to the emperor Marcian, Theodosius II having meanwhile died, and to the patriarch Anatolius. A., together with Eutherius (Asterius, according to the editors’ conjecture), bishop of Capua, and the priests Basil of Naples and Senator of Milan, was to discuss the profession of the Catholic faith by the Constantinopolitan patriarch Anatolius, formerly apocrisarius of the Alexandrian patriarch Dioscorus, successor of the deposed Flavian, and, in the event of Anatolius’s obstinacy, the convocation of a general council to be held in Italy (cf. Leo’s letters to Theodosius II and Pulcheria of 16 July 450, in Jaffé-Wattenbach, 452-53). The mission of A. and his companions succeeded: on 21 October of the same year Anatolius convened a synod, held in the baptistery of Hagia Sophia, in which all the bishops of the patriarchate were required to participate; he anathematized the doctrines of Nestorius and Eutyches and signed Leo’s Tome to Flavian.
On returning to Italy, A. and Senator brought a letter to Milan, by which Leo probably asked the bishops to make known their faith concerning the doctrines of Nestorius and Eutyches. The letter was read and signed by the suffragans of Milan, gathered
in synod by the archbishop Eusebius (first half of 451); A. also signed on behalf of the bishop of Chur. He died on 2 April in a year ranging between 462 and 489; the Bollandists hold that it was 468. He was buried in the basilica of the apostles Peter and Paul, which was later called by his name, where a fragment of the funerary slab with the inscription is still preserved (CIL, V, II, no. 5402). Cardinal Tolomeo Gallio, on 8 January 1587, had A.’s body transferred to the cathedral. His feast is celebrated on 2 April.
The Vita Abundi, published by Mombrizio (Sanctuarium, Milan 1478) and reproduced by the Bollandists, is late (7th–10th, 13th century?) and contains scanty and not always reliable biographical information; its author, however, was acquainted with the acts of the Constantinopolitan synod of 450, in which A. took part. Of this synod, hitherto known only from the Vita Abundi, P. Mouterde discovered in a Syrian manuscript in the Vatican Library and published an important fragment of its acts (Fragments d'actes d'un synode tenu à Constantinople en 450, in Mélanges de l'Université de Saint-Joseph, Beirut 1930, pp. 35-50).