1 Kings 14:25

Shishak, king of Egypt— It may seem something strange, that Shishak, who was so nearly allied to Rehoboam, should come up against him and take his royal city; but Rehoboam, we must remember, was not the son of Pharaoh's daughter, and therefore no relation to Shishak. But even had he been never so nearly related, as kingdoms, we know, never marry; so it is likely that Jeroboam, who had lived long in Egypt, stirred up Shishak to invade his rival, that he might thereby establish himself in his new kingdom: and it was for this reason, that when the armies of Egypt had taken the fenced cities of Judah, they returned without giving Jeroboam, or his dominions, the least disturbance. See Bishop Patrick.