And then the reign that opened with a request for wisdom closes with the clearest failure of it in the whole Old Testament. Solomon marries widely for political alliance — seven hundred wives, three hundred concubines, the text says, many of them from nations Israel had been explicitly warned not to intermarry with, "for surely they will turn away your heart after their gods" (1 Kings 11:1–3, quoting the warning back almost verbatim from Deuteronomy 7). Notice the shape of the failure: it isn't sudden apostasy. It's accumulation, alliance by alliance, until "his wives turned away his heart" and Solomon builds high places for Ashtoreth, Chemosh, and Molech — the very idols his own father's God had displaced (1 Kings 11:4–8). The man who asked for an understanding heart at Gibeon ends his life with a heart the text says plainly "was not perfect with the LORD his God, as was the heart of David his father" (1 Kings 11:4).
The consequence is announced directly: God tells Solomon the kingdom will be torn from his son, though for David's sake it won't happen in Solomon's own lifetime, and one tribe will be preserved for David's line "that David my servant may have a light alway before me in Jerusalem" (1 Kings 11:11–13, 36). Watch what's actually happening in that mercy — even in judgment, the unconditional covenant God made with David in 2 Samuel 7 holds. Solomon's own failure earns real consequences, but it can't undo the promise made to his father. Grace and consequence run side by side here rather than canceling each other out, the same pattern you've already seen in David's own life after Bathsheba.