“I will cut off from Jeroboam everyone.” Ahijah the prophet foretold that the house of Jeroboam would be completely destroyed, and that occurred during the reign of his son Nadab. Baasha the son of Ahijah (not Ahijah the prophet; another Ahijah) from the tribe of Issachar killed the entire house of Jeroboam, who apparently was from either the tribe of Ephraim or Manasseh (1 Kings 11:28).
“who pisses against a wall.” A crass idiom and cultural way of referring to the men, but as we learn from the verse, the women were killed also.
“he who is slave or free in Israel.” The meaning of this phrase is debated because the words themselves have a range of meanings. There are six major ideas as to what the phrase means that have been set forward by scholars. The ideas are: “slave and free men;” “those who are still under taboo and the pure;” “the controlled (or obligated) and the liberated (or independent);” “the military conscript and the one whose duty has been deferred;” “the one under the protection of the family and the one deprived of such protection;” and “the one under the authority of the father and guardian and the one released from it,” i.e., “the minor and the adult” (cp. Walter Maier III, Concordia Commentary; 1 Kings 12-22). Although the exact meaning of the phrase is not known, it is clear that it seems to refer to people who are restricted in some way and those who are not, and the point of the prophecy is that no male who is of the family of Jeroboam will escape being killed no matter what their circumstances in life. The same phrase is used in 1 Kings 21:21. See commentary on Deuteronomy 32:36.