Philip Schaff

“ The name apostles was made technical by Christ Himself: “He named them Apostles” (Luke vi. 13) . And the word is never used in the loose way which Bishop Lightfoot hazardously suggests, as I must venture to believe. ”

“ II
(Concerning Apostles, p. 380, note 16.)
The reference to “apostles,” probably itinerant, in Rev. ii. 2, corresponds with this. There were officers known in the Apostolic day (compare 2 Cor. viii. 23, Greek) as ἀπόστολοι ἐκκλησιω̑ν, for the pseud-apostles of the Apocalypse could not have pretended what they did had it been otherwise. Neither would it have been needful to “try those who said they were apostles,” in that case: the mere assertion of such a pretence would have sufficiently convicted them. ”