1 Chronicles 29:24 - Joseph Benson’s Commentary on the Old and New Testaments

And all the sons likewise of David submitted themselves unto Solomon Hebrew, gave, or put the hand under Solomon, that is, owned him for their king, and themselves for his subjects, and bound themselves by oath to be true to him, which they possibly did, according to the ancient ceremony used in swearing, mentioned Genesis 24:2; Genesis 47:29; or rather, the thing is signified by a phrase, taken from that practice formerly used, though now neglected: it being usual in all nations and languages to express present things by phrases taken from ancient customs. Though, by seniority, the title of David's other sons to the crown was prior to that of Solomon, and they might think themselves wronged by his advancement; yet, because God was pleased to make him king, and had qualified him for that high office, they all submitted themselves to him, God doubtless inclining their hearts to do so, that Solomon's reign might from the first be peaceable.