“Sarai, Abram’s wife, took Hagar the Egyptian, her maidservant, at the conclusion of ten years of Abram’s residence in the land of Canaan, and she gave her to Abram her husband as a wife” (Genesis 16:3). “Sarai, Abram’s wife, took Hagar the Egyptian, her maidservant” – she took her with words [of persuasion]. She said to her: ‘How fortunate you are, that you are going to cleave to this sacred body.’
“At the conclusion of ten years of Abram’s residence in the land of Canaan” – Rabbi Ami in the name of Reish Lakish: From where is it derived what we learned in a Mishna: If one married a woman and remained with her ten years but she did not bear any children, he is not permitted to refrain from procreation, but rather, he should divorce her and marry another woman?15Mishna Yevamot 6:6. It is from here: “At the conclusion of ten years of Abram’s residence in the land of Canaan.”
This teaches us that residence outside of the Land is not included in the tally.16As Abraham and Sarah were married many years before their ten years of residence in the land of Canaan. “And she gave her to Abram her husband” – [“to Abram”] and not to another;17Sarah wished to be “built up” by having her maidservant bear children for her. She could have accomplished this goal by giving her to any man, but she gave her specifically to Abraham. “as a wife” – and not as a concubine.