Genesis 25:21:

And Isaac intreated the LORD for his wife, because she was barren: and the LORD was intreated of him, and Rebekah his wife conceived.

Notes on Genesis 25:21:

Isaac, who lived before the Old Covenant, intreated God on his wife’s behalf and God did a miracle for Rebekah.  We have it better than Isaac or Rebekah.  All they could so was intreat God, whereas you can believe that you receive a miracle in the name of Jesus.  Healing from infertility is a covenant right you can receive as opposed to something you have to request God to do for you.

See also:

Condition: Infertility