A Tanna taught in a Baraita that the day recounted in on which Esau spurned his birthright was also the day on which Abraham died, and Jacob was cooking lentils to comfort Isaac. In the Land of Israel they taught in the name of Rabbah bar Mari that it was appropriate to cook lentils because just as the lentil has no mouth (no groove like other legumes), so the mourner has no mouth to talk but sits silently. Others explained that just as the lentil is round, so mourning comes round to all people.