Question: "Was Hagar Abraham's wife or his concubine?"
Answer: Hagar is properly considered a concubine of Abraham’s, although the Bible does call her a “wife” of Abraham in Genesis 16:3: “So, after Abram had lived ten years in the land of Canaan, Sarai, Abram’s wife, took Hagar the Egyptian, her servant, and gave her to Abram her husband as a wife” (ESV). A wife and a concubine held distinct roles in a family, but a concubine was still considered a wife of sorts.
Hagar had been Sarah’s servant, but she was raised in status to be a second wife to Abraham. This action was required for Abraham to have a child with Hagar, but it did not place Hagar on a par with Sarah (see Genesis 25:5–6); Hagar remained a secondary wife—a “slave wife,” as it were (cf. Galatians 4:21–31).
The Hebrew words for “wife” and “concubine” are different, but the word for “wife” has a broad range of meanings and can be translated as “woman,” “wife,” or “female.” The word was not always used with precision. That’s why, in Genesis 16:3, both Sarah and Hagar are called a “wife” of Abraham, using different forms of the same Hebrew word. The broad definition of the word in question means we have to use context clues to more precisely define it. In Hagar’s case, her status as Sarah’s slave means that she was a “wife” of a lesser class. In biblical times there were various rankings of wives, but the first wife always had seniority.
It is worth noting that, after Sarah died, Abraham married again: “Abraham had taken another wife, whose name was Keturah” (Genesis 25:1). Elsewhere, Keturah is called Abraham’s “concubine” (1 Chronicles 1:32); so, Keturah was both. She was a wife, but she was of an inferior status to Sarah. The same could be said of Hagar.
Abraham had a principal wife, Sarah, and two secondary wives, Hagar and Keturah. Sarah alone possessed legal rights and social standing as Abraham’s wife, and only her child, Isaac, was the rightful heir to the family inheritance (see Genesis 25:5). Sarah, who had been unable to bear children, gave her Egyptian servant, Hagar, to Abraham as a concubine/wife. Taking a concubine was a common solution to childlessness in ancient times. But a concubine only held “secondary wife status.”
God had plans for Hagar and her child by Abraham. God dealt kindly with both Hagar and Ishmael, preserving their lives and making Ishmael the father of a great nation (Genesis 21:8–21).