Genesis 29:27-31

But complete the full week of the marriage ceremony with Leah, and I will give you Rachel to marry also. But you must serve me another seven years.” So Jacob did this, and when he had completed the week with Leah, Laban gave him his daughter Rachel as a wife. (Laban gave his slave girl Bilhah to his daughter Rachel to be her servant.) So Jacob had sexual relations with Rachel also, and Jacob loved Rachel more than Leah. Jacob worked for Laban for another seven years. When the LORD saw that Jacob loved Rachel more than Leah, he made it possible for Leah to have children, but not Rachel.