Lentils are mentioned many times in the Old Testament . In Jewish tradition they are considered as food for mourners , together with boiled eggs . Lentils are mentioned many times in the Old Testament , the first time recounting the incident in which Jacob purchases the birthright from Esau with stewed lentils ( a `` mess of pottage '' ) In Jewish mourning tradition , they are considered as food for mourners , together with boiled eggs .