The NT refers to Christians as the heirs of the OT promises to Israel (Gal 3:26-29; 6:16) and as “the twelve tribes scattered in the diaspora” (James 1:1; cf. 1 Pet 1:1)
The Son of David goes off to war with the Evil One, who tempts and assaults God’s people night and day. He fights to win and defend you, God’s people. Jesus is a man after God’s own heart, that is, doing the Father’s will. All the might of God’s enemies comes unraveled in Israel’s eternal Messiah king, Jesus.
The indwelling of the Glory of Yahweh in the temple was necessary for the life-giving water to flow from the temple, and that indwelling points to the incarnation of Christ, “in whom all the fullness of the Deity dwells bodily” (Col 2:9). The water flows past the altar because the sacrificial atonement by Christ was necessary for the new life brought by the river to come to the dead and barren creation. The river is a prefiguration of Christian Baptism, following the LXX “water of forgiveness.” The same word for brook or stream can be translated as “release” and is used in the NT for forgiveness or remission of a debt, as in the Words of Institution and Baptism proclamation.