Marriages of Israelites with women of Ammon or Moab are nowhere in the Law expressly forbidden, as were marriages with the women of Canaan Deuteronomy 7:1-3. In the days of Nehemiah the special law Deuteronomy 23:3-6 was interpreted as forbidding them, and as excluding the children of such marriages from the congregation of Israel Nehemiah 13:1-3. Probably the marriages of Mahlon and Chilion would be justified by necessity, living as they were in a foreign land. Ruth was the wife of the older brother, Mahlon Ruth 4:10.
Related Commentaries of Ruth 1:4
Ruth 1:4
4 And they took them wives of the women of Moab; the name of the one was Orpah, and the name of the other Ruth: and they dwelled there about ten years.