Ethan announced two major themes of this psalm in Psalm 89:1-2. These are the loyal love (Heb. hesed) and faithfulness of Yahweh. References to God"s loyal love occur in Psalm 89:1-2; Psalm 89:14; Psalm 89:24; Psalm 89:28; Psalm 89:33; Psalm 89:49. He referred to God"s faithfulness in Psalm 89:1-2; Psalm 89:5; Psalm 89:8; Psalm 89:24; Psalm 89:33; Psalm 89:49. He proceeded to appeal to God to honor His promises to David on the basis of these qualities. [source][source][source]
The psalmist restated the Davidic Covenant promises in Psalm 89:3-4. Interestingly the word "covenant" does not occur in either2Samuel7 or1Chronicles17 , the two places in the Old Testament where God recorded the giving of that covenant. Three key terms used in these two verses also recur throughout this psalm. These are "covenant" ( Psalm 89:3; Psalm 89:28; Psalm 89:34; Psalm 89:39), "David My servant" ( Psalm 89:3; Psalm 89:20; Psalm 89:50 where it is just "My servant"), and "throne" ( Psalm 89:4; Psalm 89:14; Psalm 89:29; Psalm 89:36; Psalm 89:44). Obviously the Davidic Covenant was central in the writer"s thinking in this psalm. [source][source][source]
"The background for the Davidic Covenant and the sonship imagery associated with it is the ancient Near Eastern covenant of grant, whereby a king would reward a faithful servant by elevating him to the position of "sonship" and granting him special gifts, usually related to land and dynasty. Unlike the conditional suzerain-vassal treaty, after which the Mosaic Covenant was patterned, the covenant of grant was an unconditional, promissory grant which could not be taken away from the recipient. [1] Weinfeld, "The Covenant of Grant in the Old Testament and in the Ancient Near East," [2] pp184-203 , for a thorough study of this type of covenant and its biblical parallels, including the Davidic Covenant. ..."] Consequently God"s covenantal promises to David were guaranteed by an irrevocable divine oath ( Psalm 89:3; Psalm 89:28-37; Psalm 132:11)." [3][source]