Isaiah 59 ends with Yahweh’s pledge of covenant faithfulness (v. 21). “This is my covenant with them.” What is that covenant?
Two things: Spirit and words. Yahweh’s Spirit is “upon you” (cf. Isaiah 11:2; 42:1) His words are “in your mouth.”
Spirit and words are given forever: “they shall not depart . . . from now to forever.”
Spirit and words are transmitted from generation to generation: They shall not depart “from the mouth of your seed, nor from the mouth of your seed’s seed.”
A Christian reading of this passage can hardly miss the Trinitarian overtones. This is the covenant of God, that He gives His Spirit and His eternal Word to His people from generation to generation, and that by giving His Spirit and Word, He places His words, like a burning coal, in the mouth of His people.