Apostle, 'one commissioned,' represents a Heb. word which signified not merely a messenger but a delegate, bearing a commission, and, so far as his commission extended, wielding his commissioner's authority. 'The Apostle of any one,' says the Talmud, 'is even as the man himself by whom he is deputed.' The term was applied by Jesus to the twelve disciples whom He attached to Himself to aid Him in His ministry and to be trained by the discipline of His example and precept for carrying it on after His departure (Lu 6:13; Mt 10:2). Cf. Joh 17:18 'Even as thou didst commission me unto the world, I also commissioned them unto the world' (where 'commission' is the verb cognate to 'Apostle').
Jesus appointed twelve Apostles corresponding to the twelve tribes, thus intimating that their mission was meanwhile to Israel (cf. Mt 10:5-6); but by and by, when He was setting out on His last journey to Jerusalem, He 'appointed other seventy and commissioned them' (Lu 10:1), thus intimating the universality of His gospel, inasmuch as, according to Jewish reckoning, mankind was composed of seventy nations.
After the Lord's departure the Twelve were the Apostles par excellence (cf. Ac 6:2,6). They were the men who had been with Jesus, and their peculiar function was to testify of Him, and especially of His Resurrection (Ac 1:21-22; cf. Ac 1:8 and Lu 24:48). But they were not the only Apostles. The title was given to Barnabas (14/4/type/hcsb'>Ac 14:4,14; 1Co 9:5-6) and Andronicus and Junias (Ro 16:7). It may be that it was extended to men of Apostolic character, but then why was it withheld from one like Timothy (2Co 1:1; Col 1:1)? If Barnabas, as tradition declares, and Andronicus and Junias, as Origen suggests, belonged to the order of the Seventy, it may well be that those others besides the Twelve who were styled 'Apostles' were the Seventy. It is true the title is given to James the Lord's brother (Ga 1:19; 1Co 15:7) and to Paul, who belonged neither to the Twelve nor to the Seventy. But theirs were exceptional cases. It was natural that James, who was recognized as the head of the Church at Jerusalem, should be accorded the dignity of Apostleship, as well for his extreme sanctity as for his relationship to Jesus. And as for Paul, his Apostolic title was bitterly contested; and he triumphantly defended it on the double ground that, though he had not companied with Jesus in the days of His flesh, he had seen Him after His glorification on the road to Damascus (1Co 9:1), and though he was not one of the original Apostles, his Apostleship had the Lord's own sanction (1Co 9:2; 2Co 12:12). Perhaps it was his example that emboldened others outside the ranks of the Twelve and the Seventy to claim Apostleship on the score of Apostolic gifts, real or supposed (2Co 11:13; Re 2:2). See also Disciples.