God's instruction through Moses in Deuteronomy 17:17 leaves little room for interpretation or doubt. Israel's leader was not to "multiply wives to himself." Solomon may have subconsciously reasoned, "If importing horses from Egypt has brought no immediate penalty, what is the harm of taking a second wife?" Yet he eventually took a third, a fourth, a fifth, and so on. Each new wife confirmed his decision to violate God's law.
By the end of his reign, he had 700 wives, not to mention an additional 300 mistresses or concubines (I Kings 11:3)! God's prohibition of royal bigamy was a means of protecting the king from having his heart turned away from Him. Solomon failed to heed this wise principle.
He compounded the problem even further by marrying,
many foreign women, as well as the daughter of Pharaoh: women of the Moabites, Ammonites, Edomites, Sidonians, and Hittites—from the nations of whom the LORD had said to the children of Israel, 'You shall not intermarry with them, nor they with you'" (verses 1-2).
In Deuteronomy 7:3-4, Moses predicts the deadly results of marrying non-Israelite women: Such wives would lead their husbands "to serve other gods." Solomon disregarded these warnings. When he was old, he allowed his foreign wives to turn his heart "after other gods; and his heart was not loyal to the LORD his God" (I Kings 11:4).
From the "minor" infraction of importing horses from Egypt, he eventually condoned, or at least was an accessory to, the sins of idolatry and murder, sins he would not have contemplated seriously at the beginning of his reign.
Solomon not only "went after Ashtoreth the goddess of the Sidonians, and after Milcom the abomination of the Ammonites" (verse 5), but he also "built a high place for Chemosh the abomination of Moab, . . . and for Molech, the abomination of the people of Ammon" (verse 7), whose rituals involved the horrible rite of child sacrifice by fire (Leviticus 18:21; Jeremiah 32:35). Archaeologists have found skeletal remains of infants at three sites where this brutal human sacrifice occurred. These Solomonic high places for Chemosh and Molech stood for three centuries before Josiah finally destroyed them (II Kings 23:10, 13).
As a result of Solomon's perverted disobedience, several of his corrupt successors to the throne even caused their children to "pass through the fire" (II Kings 16:3; 21:6). How degenerate can someone be to sacrifice his own child as a burnt offering to Satan's idolatrous creations?
— Martin G. Collins