Dunn on Israel in the New Testament

"The fact that Israel remains a given for the NT is very striking, not least in view of the fact that by the end of the first century embryonic Christianity must already have been predominantly Gentile in composition. But fundamental it was. Jesus' message can be summed up in terms of a hope for the restoration of Israel. The first believers were all Jews, and the great majority of the NT writings were composed by Jews. The Paul of Acts sums up his mission by reference to ‘the hope of Israel’ (Acts 28:20), just as the Paul of Romans affirms the irrevocability of God’s calling of Israel and purpose for Israel (Rom 1 1:25–32). The chief term for Christian congregations, ‘church’ (ekklēsia), has been taken over from the LXX's translation of the qahal YHWH or the qahal lsrael (qahal = ‘assembly, congregation’).The assumption of the opening verses of James and 1 Peter is that the letters were addressed to (the twelve tribes[!] of) the Diaspora. And the seer of Revelation envisages salvation as embracing 144,000, 12,000 from each of the twelve tribes of Israel (Rev 74–8)."

James D. G. Dunn, New Testament Theology: An Introduction, Library of Biblical Theology, ed. James D. G. Dunn (Nashville: Abingdon, 2009), 97–8.