Yea, all kings shall fall down before him: all nations shall serve him. All kings shall fall down before - They shall reverence him on account of his great wisdom, riches, etc.
All nations shalt serve him - All the surrounding nations. This and the preceding verses are fully explained by 1 Kings 10:23-25 : "King Solomon exceeded all the kings of the earth for riches and for wisdom. And all the earth sought unto Solomon to hear his wisdom. And they brought every man his present, vessels of silver, and vessels of gold, and garments and armor, and spices, horses and mules a rate year by year." If we take these expressions to mean literally all the habitable globe, then they cannot be applied to Solomon; but if we take them as they are most evidently used by the sacred writer, then they are literally true. When all the earth shall be brought to receive the Gospel of Christ, then they may be applied to him.