Cease to hear instruction, my son, and you will stray from the words of knowledge.
Solomon stopped listening to wisdom. He took what was expedient, easy, customary. We stop listening to God:
23 In those days also I saw the Jews who had married women of Ashdod, Ammon, and Moab.
24 And half of their children spoke the language of Ashdod, and they could not speak the language of Judah, but only the language of each people.
25 And I confronted them and cursed them and beat some of them and pulled out their hair. And I made them take oath in the name of God, saying, “You shall not give your daughters to their sons, or take their daughters for your sons or for yourselves.
26 Did not Solomon king of Israel sin on account of such women? Among the many nations there was no king like him, and he was beloved by his God, and God made him king over all Israel. Nevertheless, foreign women made even him to sin.
27 Shall we then listen to you and do all this great evil and act treacherously against our God by marrying foreign women?”
Neh. 13:23-27. This has nothing to do with ethnicity. Ruth, Tamar, Rahab are all in the Messiah’s line. It is being joined to the world which is in rebellion against God. It is for this reason that we exhort one-another everyday.