The Christian Gospels of Mark and Matthew say that, after the Ascension of Jesus, his Apostles "went out and preached everywhere". This is described in Mark 16 verses 19 and 20, and Matthew 28 verses 19 and 20. According to a tradition mentioned by Eusebius, they dispersed to distinct parts of the world. In the Middle Ages a liturgical feast of the Dispersion of the Apostles was celebrated to commemorate their missionary work and their founding the apostolic sees. This annual feast was held on 15 July and ranked as a major double.
The Acts of the Apostles, the canonical sequel to the Gospel of Luke, portrays the dispersal as occurring a substantial time after the ascension, with the ministry staying in Jerusalem at first and spreading from there beginning with the conversion of the Ethiopian eunuch.
According to Book 3 of the Church History of Eusebius:
Meanwhile the holy apostles and disciples of our Saviour were dispersed throughout the world. Parthia, according to tradition, was allotted to Thomas as his field of labor, Scythia to Andrew, and Asia to John, who, after he had lived some time there, died at Ephesus. Peter appears to have preached in Pontus, Galatia, Bithynia, Cappadocia, and Asia to the Jews of the dispersion. And at last, having come to Rome, he was crucified head-downwards; for he had requested that he might suffer in this way. What do we need to say concerning Paul, who preached the Gospel of Christ from Jerusalem to Illyricum, and afterwards suffered martyrdom in Rome under Nero? These facts are related by Origen in the third volume of his Commentary on Genesis.
Arthur Cushman McGiffert comments:
According to Lipsius, the legends concerning the labors of the apostles in various countries were all originally connected with that of their separation at Jerusalem, which is as old as the second century. But this separation was put at various dates by different traditions, varying from immediately after the Ascension to twenty-four years later.