So great is circumcision that thirteen covenants were made concerning it. Tosafoth says that covenant is written thirteen times in the chapter of circumcision.
Rabbi (the Holy) says sufferings are to be borne with resignation. He himself bore them submissively for thirteen years; for six he suffered from lithiasis, and for seven years from stomatitis (or, as some say, six years from the former and seven from the latter). His groans were heard three miles off.
The Rabbis have taught thirteen things respecting breakfast (morning-morsel):--It counteracts the effects of heat, cold or draught; it protects from malignant demons; it makes wise the simple by keeping the mind in a healthy condition; it enables a man to come off clear from a judicial inquiry; it qualifies him both to learn and to teach the law; it makes him eagerly listened to, to have a retentive memory, etc.
The land of Israel is in the future to be divided among thirteen tribes, and not, as at first, among twelve.
Rabbi Abhu once complimented Rav Saphra before the Minim by singling him out in their hearing as a man distinguished by his learning, and this led them to exempt him from tribute for thirteen years. It so happened that these Minim once posed Saphra about that which is written in Amos iii. 2, "You only have I known of all the families of the earth; therefore I will punish you for all your iniquities." "Ye say you are God's friends, but when one has a friend does he pour out his wrath upon him?" To this Rav Saphra make no reply. They then put a rope round his neck and tormented him. When he was in this sorry plight, Rabbi Abhu came up and inquired why they tormented him thus. To this they made answer, "Didst thou not tell us that he was a very learned man, and he does not even know how to explain a text of Scripture?" "Yes, I did so say," replied Rabbi Abhu; "he is an adept in the Talmud only, but not in the Scriptures." "Thou knowest the Scriptures;" they replied, "and why ought he not to know them as well?" "I have daily intercourse with you," said the Rabbi, "and therefore I am obliged to study the Scriptures, but he, having no intercourse with you, has no need to trouble himself, and does not at all care about them."