While Christian tradition often refers to the apostles as being twelve in number, different gospel writers give different names for the same individual, and apostles mentioned in one gospel are not mentioned in others. The commissioning of the Twelve Apostles during the ministry of Jesus is recorded in the Synoptic Gospels. After his resurrection, Jesus sent eleven of them (minus Judas Iscariot, who by then had died) by the Great Commission to spread his teachings to all nations. This event is commonly called the Dispersion of the Apostles. There is also an Eastern Christian tradition derived from the Gospel of Luke of there having been as many as 70 apostles during the time of Jesus' ministry. Prominent figures in early Christianity, notably Paul, were often called apostles, even though their ministry or mission came after the life of Jesus.
The period of early Christianity during the lifetimes of the apostles is called the Apostolic Age. During the 1st century AD, the apostles established churches throughout the territories of the Roman Empire and, according to tradition, through the Middle East, Africa, and India.
The word "apostle" comes from the Greek word ἀπόστολος (apóstolos), formed from the prefix ἀπό- (apó-, "from") and root στέλλω (stéllō, "I send", "I depart") and originally meaning "messenger, envoy". It has, however, a stronger sense than the word messenger, and is closer to a "delegate". The Greek-English Lexicon of the New Testament argues that its Christian use translated a Jewish position known in Hebrew as the sheliach (שליח). This ecclesiastical meaning of the word was later translated into Latin as missio, the source of the English "missionary".
In the New Testament, the names of the majority of the apostles are Hebrew names, although some had Greek names. Even Paul, the "apostle of the Gentiles", who said that Jesus revealed himself to him only after his ascension and appointed him to his mission, was a Jew by birth and proud of it, although after his conversion he adopted the Roman cognomen Paulus, rendered in English as Paul, as his name. Paul claimed with much insistency this title and its rights, and made the case to the Corinthian Church that he was an apostle by the evidence of the fruits of his ministry, of which they themselves were.
Mark 6:7–13 states that Jesus initially sent out these twelve in pairs (cf. Mt 10:5–42, Lk 9:1–6) to towns in Galilee. The text states that their initial instructions were to heal the sick and drive out demons. They are also instructed to "take nothing for their journey, except a staff only: no bread, no wallet, no money in their purse, but to wear sandals, and not put on two tunics", and that if any town rejects them they ought to shake the dust off their feet as they leave, a gesture which some scholars think was meant as a contemptuous threat (Miller 26). Their carrying of just a staff (Matthew and Luke say not even a staff) is sometimes given as the reason for the use by Christian bishops of a staff of office in those denominations that believe they maintain an apostolic succession.