This refers to David's desire to build the Temple. When David became king, he built a beautiful palace, but he was troubled that the Ark of the Covenant, the symbol of God's presence among his people (Exo 25:10-22), remained in a tent (2Sa 6:17; 2Sa 7:1-17). This so bothered David that he couldn't sleep until he corrected the situation. He began to lay the plans for the Temple to house the Ark. (Eventually the Temple was built by his son Solomon.) We must live so close to God that we become restless until God's will is accomplished through us.
Psalms 132:11-12
The promise that David's sons would sit on Israel's throne forever is found in 2Sa_7:8-29. This promise had two parts: (1) David's descendants would perpetually rule over Israel as long as they followed God, and (2) David's royal line would never end. The first part was conditional: As long as the kings obeyed God ("obey the terms of my covenant"), their dynasty continued. The second part of the promise was unconditional: It was fulfilled in Jesus Christ, a descendant of David, who reigns forever.
Psalms 132:17-18
The "increase" of David's power refers to one of his mighty descendants. David's son Solomon was indeed a glorious king (1Ki 3:10-14); but these verses look ahead even further to another descendant of David, Jesus the Messiah (Mat 1:17). The power, might, and glory of the Messiah will last forever.
