The verse before us now repeats the geographical extent of Solomon’s reign, but it also adds some information. Previously we were told that other nations (and their kings) paid tribute to Solomon. Here we learn that he literally ruled over them. The Hebrew root is the word radach, which means to have dominion, to rule.
Solomon, in truth, had an empire over which he exercised sovereign authority.
An independent nation could pay tribute to a foreign monarch while still retaining much of its sovereignty. As long as the tribute flowed to the overlord, the rulers of the tributary states could see to their own affairs.
We must understand that the kings mentioned here were what we might call puppet kings. They were subject, not only to Solomon’s taxation but also to his commands. He was king over other kings.
24 For he had dominion over all the region west of the Euphrates from Tiphsah to Gaza, over all the kings west of the Euphrates. And he had peace on all sides around him.