What is the difference between a wife and a concubine?

Question:

In Deuteronomy 21, after a war in the Old Testament, it says that if you wish to make a woman your wife, you must shave her head and cut her nails, etc., but what if he wanted to make her a concubine? Was this permitted or not? Deuteronomy doesn't say anything at all about this.

Answer:

A concubine is a slave woman who becomes a man's wife. For example, "After Abram had lived ten years in the land of Canaan, Abram's wife Sarai took Hagar the Egyptian, her maid, and gave her to her husband Abram as his wife" (Genesis 16:3). Later, Abraham married another slave woman. "Now Abraham took another wife, whose name was Keturah" (Genesis 25:1). However, she was also referred to as Abraham's concubine. "The sons of Keturah, Abraham's concubine, whom she bore, were Zimran, Jokshan, Medan, Midian, Ishbak and Shuah. And the sons of Jokshan were Sheba and Dedan" (I Chronicles 1:32).

Those taken in wars became slaves in Israel. These women, when old enough, were eligible for marriage. "When you go out to war against your enemies, and the LORD your God delivers them into your hand, and you take them captive, and you see among the captives a beautiful woman, and desire her and would take her for your wife, then you shall bring her home to your house, and she shall shave her head and trim her nails. She shall put off the clothes of her captivity, remain in your house, and mourn her father and her mother a full month; after that you may go in to her and be her husband, and she shall be your wife" (Deuteronomy 21:10-13). Thus, these women would be concubines -- slave women who were made wives.