1 Kings 11:13 - Matthew Poole's English Annotations on the Holy Bible

How but one tribe, when he had both Judah and Benjamin, 2 Chronicles 11:12 ? Answ. Either Benjamin is swallowed up in Judah, because it was comparatively very small, and their habitation much intermixed with that of Judah: or one, to wit, of that kingdom which he here threatens to rend away from him, i.e. of the kingdom of Israel, and that was Benjamin; one beside Judah, which was his own tribe: or but one, because Benjamin was not entirely his, but part of it adhered to Jeroboam, as Beth-el, 1 Kings 12:29, and Ephrain, 2 Chronicles 13:19, both which were towns of Benjamin, Joshua 18:22. Or if God promised to give one, and gave him two, I suppose that was no great injury to him. For Jerusalem's sake; not, surely, for its merits; but because he had chosen it, as it follows, to be the seat of his temple and worship; it being God's usual method to give to him that hath, and to continue and multiply favours to them whom he hath begun to favour.