The choice of seven men in Acts 6:1-6 describes a climactic moment in the history of the Church. The Greek speaking widows, who do not attend the Temple in Jerusalem where the Apostles preach, need an explanation in their own language in their own homes (cf. Ac 6:2 “to serve tables” [RSV accurately rendering the Greek which has no preposition]). In Are all Christians Ministers? p. 39, John Collins notes that Luke’s omission of the preposition points up the difference between ministering at tables and ministering in the vicinity of tables, something that the Apostles cannot do because their priority is to preach in the surrounds of the temple. The Apostles lay hands on seven men for this ministry.
The work of the seven in the Church at Jerusalem is named a diakonia. This is the word used in the New Testament to describe the commission received from God by apostles, prophets and teachers to proclaim and explain the good news of the saving love of God in Christ through the Spirit.
With much opposition from the authorities, Peter and John had been preaching the Good News in the Temple (Ac 5:40-42). This is their diakonia (Ac 1:17, 25) performed in obedience to Jesus’ parting command (Ac 1:8).
The seven chosen men go out and preach too, as we hear in Stephen’s testimony before he is stoned to death (Ac 7) and in Phillip’s journey through Samaria (Ac 8). In Ac 6, the seven Greek-speaking men are not called “deacons” (diakonoi). However, they perform a “daily diakonia” (Ac 6:1) for the Greek-speaking widows so that the Twelve are free to continue with their diakonia of preaching (Ac 6:4). Many, though not all, modern biblical translators have rendered the Greek word diakonia in Ac 6:1 as “service” of the needy widows, even though everywhere else the word refers to the sacred task of preaching.
Acts of the Apostles relates that St Paul at Ephesus summed up his missionary work as the diakonia of testifying to the good news (Ac 20:24).