Once Rabbi Elazar son of Rabbi Shimon was coming from Migdal Gedor, from the house of his teacher. He rode along the riverside on his donkey, and was feeling happy and elated because he had studied much Torah. There chanced to meet him an exceedingly ugly man, who greeted him, "Peace be upon you, my master!" Rabbi Elazar did not return his salutation but instead said to him, "How ugly this person is! Are all the people of your city as ugly as you?" "I do not know," said the man. "But go to the craftsman who made me, and say to him: How ugly is the vessel which you have made!" Realizing that he had done wrong, Rabbi Elazar dismounted from his donkey, prostrated himself before the man, and said to him, "You are right. Forgive me!" But the man replied, "I will not forgive you until you go to the craftsman who made me and say to him, 'How ugly is the vessel which you have made.'" -Ta’anit 20a