Luke introduced Cornelius to Peter by summarizing the earlier introduction in words suitable for Jewish ears: Cornelius remains φοβουμενος τον Θεον but now he is δικαιος rather than the ‘strange’ ευσεβης, and it is hard not to see δικαιος here as a distillation of ‘generous almsgiving and diligent prayer by one who reverences God’. The wider Jewish community would also give Cornelius a good reference—mαρτυρουμενος τε υπο ολου του εθνους των ‘Ιουδαιων (Acts 10.22). The unambiguous statement that ‘Cornelius is δικαιος’ must not be undervalued; it has been carefully explored by Like and encapsulates the principle adumbrated by Peter at Acts 10.34-5, namely that God is not to be thought of as interested only in ethnic Jews, but accepts Gentiles who reverence him and behave consonantly with that reverence. Luke has taken such pains over the Cornelius story that a reader must ask what might have been happening in Luke’s church to evoke such careful writing about the place of Gentile converts in God’s economy of salvation. One must assume a corpus mixtum living with tensions deriving from divergent ways of understanding God’s will . . . Luke helps these groups grasp the ασφαλειαν των πεπληροωορημενων ων ημιν πραγματων (Luke 1.1-4) by detailing the things concerning Cornelius.
Just as Zechariah and Elizabeth, then Simeon and, later, Joseph were representatives of Israel’s patient, faithful piety, so Cornelius epitomized those ‘among the nations’ whose hope would also be realized by God’s saving acts in Jesus and who might properly be called δικαιος. Further, God has spoken to Cornelius as to Simeon and to Zachariah. For Simeon the word has come by holy spirit:
καὶ ἦν αὐτῷ κεχρηματισμένον ὑπὸ τοῦ πνεύματος τοῦ ἁγίου μὴ ἰδεῖν θάνατον πρὶν ἢ ἂν ἴδῃ τὸν χριστὸν κυρίου.
For Cornelius as for Zechariah, the word of God came by angelic vision:
. . . εχρηματισθη υπο αγγελου αγιου . . .
(Acts 10.22b cf. Luke 1.8-20)
Thus, by his reverencing God, by his virtues and by an angelophany Cornelius was installed among Luke’s δικαιοι. (Peter Doble, The Paradox of Salvation: Luke’s Theology of the Cross [Society of New Testament Studies Monograph Series 87; Cambridge: Cambridge University Press, 1996], 106-7)