"... In the seventh beatitude, blessedness is pronounced on the peacemakers, because “they will be called children of God”. The lexical study of the peacemakers in the preceding section shows that while peacemakers may refer to those who reconcile, it can also be used more broadly to refer to those who create shalom. There is further evidence from rabbinic and Jewish wisdom literature to show that peacemaking primarily refers to concrete steps to promote harmony within interpersonal relationships. (e.g. 2 Enoch 52:11–13; Mekhilta on Exodus 20:25) Understood in this manner, peacemaking goes beyond non-violence or passively maintaining a state where hostility is absent; it is an active pursuit of harmonious relationships as intended by God. Generally speaking, peacemaking is not mediating peace between other people, but initiating one’s own peace with others. For this reason, an examination of Jesus’ teachings about interpersonal relationships in Matthew may provide hints as to what is intended by the “peacemakers” in 5:9. Within the Sermon on the Mount itself, there are at least three teachings concerning interpersonal relationships - Matthew 5:23, 5:38–42, and 5:43–48 - which are closely related to the idea of peacemaking in 5:9. They have to do with reconciliation and forgiveness, revenge, and loving one’s enemies ..."

Lo, Jonathan W. Sharing the Blessing of the Peacemaker: An Exegetical Analysis of Matt 5:9 (pp. 1-15) Hill Road Journal, 2014