οἷς καὶ παρέστησεν ἑαυτὸν ζῶντα μετὰ τὸ παθεῖν αὐτὸν ἐν πολλοῖς τεκμηρίοις, δι’ ἡμερῶν τεσσεράκοντα ὀπτανόμενος αὐτοῖς καὶ λέγων τὰ περὶ τῆς βασιλείας τοῦ θεοῦ·

Translation: And he presented himself to them alive after his suffering by many proofs. He was seen by them forty days and spoke about the kingdom of God.

Just after the resurrection, Jesus tells the early Church about τῆς βασιλείας τοῦ θεοῦ, the kingdom of God. Luke talks about the Kingdom of God approximately 44 times in his writings. Its very first occurrence is found in Luke 1:33, when the birth of Jesus is proclaimed to Mary by the angel Gabriel: “He will reign over the house of Jacob forever, and his kingdom will never end.” From the start, God’s Kingdom is identified with the person of Jesus. Through Jesus, God executes His reign in the world. During his life, Jesus’ preaching focuses on the Kingdom and in His miracles, the presence of the Kingdom is seen (Luke 9:2). The Kingdom is proclaimed, but it also requires action and pursuit (Luke 12:31). The task of proclaiming the kingdom is then passed on to the Apostles in the book of Acts. Throughout the book, Luke presents the Apostles as preaching the Kingdom of God, as it is revealed in Jesus (Acts 8:12). Yet even for the Apostles, it is not just preaching, but is lived out as they faithfully endure persecution (Acts 14:22). Throughout Luke’s writings, he presents the Kingdom as a new reality which must be lived and the good news of its arrival must be proclaimed to all so that all might enter its life.