– I am hesitant to speak of Pentecost as “the birth of the church,” since this seems foreign to the Lukan message. If by “church” we mean followers of Jesus, then there have been followers before Pentecost. If by “church” we mean one group including Jews and non-Jews, then we are finding something in the narrative that doesn’t occur until several chapters later. It seems more appropriate to see Pentecost as the full inauguration of the New Covenant as depicted by the availability of the Spirit to all people, not a select few.
– It should be observed that this is not the first time people are filled with the Spirit. In Luke 1:15 John the Baptist is filled with the Spirit in his mother’s womb. In 1:41 Elizabeth is filled with the Spirit. In 1:67 Zacharias is filled with the Spirit. Old Covenant figures such Bezalel (Exodus 31:3; 35:31), Joshua (Deuteronomy 34:9), and Micah (3:8) receive the Spirit before Pentecost. This doesn’t detract from Pentecost, because Pentecost is the “democratization” of the Spirit (if you will). Moses imagined a day when all the people of God might be prophets (Numbers 11:29). In some sense (not to ignore that the New Covenant seems to include a new role of prophet distinct from that of the Old Covenant) Pentecost does make all the people of God a prophetic people. Similarly, as the prophet Joel foresaw, the Spirit would be poured out upon all sorts of people, many marginalized by society, including daughters and slaves (2:28-29). The apostle Peter interpreted the Day of Pentecost to be the fulfillment of Joel’s vision (Acts 2:16-21, though the exact nature of Peter’s interpretation is not as clear as we might like in that he includes much of the apocalyptic imagery).
– If we read Luke 24:49; Acts 1:4; 2:33; 13:23, 32 we find that Pentecost is a fulfillment of the Old Covenant: the Spirit has been “poured out” upon people; the Messiah have been revealed (through the resurrection). Pentecost is connected to the resurrection of Jesus as the two stage beginning of the “already, but not yet,” the eschaton before the eschaton.