Genesis 16:3 (BSB)

So after he had lived in Canaan for ten years, his wife Sarai took her Egyptian maidservant Hagar and gave her to Abram to be his wife.

From Genesis 16. Also in the ESV.

Commentary on Genesis 16:3

• John Calvin (Reformed), Calvin's Commentaries on Genesis 16:3: 3. And gave her to her husband Abram to be his wife . Moses states what was the design of Sarai; for neither did she intend to make her house a brothel, nor to be the betrayer of her maid’s chastity, nor a pander for her husband. Yet Hagar is improperly called a wife; because she was brought into another person’s bed, against the law of God.
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Genesis 16:1-3: We have here the marriage of Abram to Hagar, who was his secondary wife. Herein, though some excuse may be made for him, he cannot be justified, for from the beginning it was not so; and, when it was so, it seems to have proceeded from an irregular desire to build up families for the speedier peopling of the world and the church. Certainly it must not be so now.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Genesis 16:3: And Sarai, Abram's wife, took Hagar her maid, the Egyptian,.... Took her by the hand, it is probable, and led her into the apartment where Abram was, and presented her to him; their characters are very exactly described, and the contrast beautifully given, that the affair might be the more remarkable and observable: after Abram had dwelt ten years in the land of Canaan; so...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Genesis 16:3: Sarai . . . gave her to . . . Abram to be his wife--"Wife" is here used to describe an inferior, though not degrading, relation, in countries where polygamy prevails. In the case of these female slaves, who are the personal property of his lady, being purchased before her marriage or given as a special present to her, no one can become the husband's...