Parsha Vayetzei – Chapter 30 – Verse 14-15
Reuven was in the field, and he tied his donkey to a bush. When he came back to the donkey, he saw the donkey was dead. This bush was called dudaim (mandrake), was a sought after plant, as these flowering herbs were thought to enhance a woman’s fertility. It was very hard to come by because whoever pulled it out of the ground died. Reven took the mandrakes and brought them to his mother. Leah & Rachel, then argued over the mandrakes. Leah said, you took my husband, and now you want these. This argument proves to us the greatness of Rachel's deed because of not only in what she did for Leah, but even more so in the way she did it. It is considered the greatest act in the world to come.
Finally they came to an agreement. Leah would give Rachel some of the mandrakes as a trade for allowing Leah to sleep with their husband, Yaakov that night.