Rashi on Genesis 16:1/רש"י על בראשית ט״ז:א׳

1שפחה מצרית A HANDMAID, AN EGYPTIAN — She was a daughter of Pharaoh; when he saw the miracles which had been performed for Sarah’s take he said, “It is better for my daughter to be a handmaid in this man’s house than be mistress in another man’s house” (Genesis Rabbah 45:1).