The Basis of the Halakha
יסוד ההלכה
The Talmud in tractate Kiddushin (31a) relates that Rav Huna son of Rav Yehoshua would not walk four amot with his head uncovered. For he said: “The Shekhina is above my head; how can I walk with my head uncovered?”
The kippa delimits, as it were, the boundary of the person, and reminds him that there is One above him. Tractate Shabbat (156b) relates that the astrologers told the mother of Rav Naḥman bar Yitzḥak, while he was still an infant, that according to the wisdom of the constellations it was absolutely clear that her son was destined to be a thief. In order to prevent the fulfillment of the constellation, the mother instructed her son to always be careful to wear a covering on his head, so that the fear of Heaven would be upon him, and she likewise made sure that he would always pray for mercy that the evil inclination not rule over him. Rav Naḥman did not know why his mother was so insistent about his head covering, until one time the covering fell from his head, and he raised his eyes and saw a cluster of dates on a palm tree. Although the palm tree was not his, he desired the dates and could not overcome his inclination, and he climbed the palm tree with his hands and bit into the dates with his teeth. After he felt the strength of his inclination to steal, Rav Naḥman understood why his mother had been so insistent that he always cover his head.
From the perspective of halakha, wearing a kippa began as a custom of piety (minhag ḥasidut), in that some of the Sages were careful not to walk four amot without a head covering, in order to arouse themselves to the fear of Heaven. Over time the custom spread throughout Israel, until it left the category of a custom of piety and became a binding custom not to walk more than four amot without a head covering. And it is a custom of piety not to walk even less than four amot without a kippa (MA OḤ 2:6).
Even when there is a strong wind and the kippa cannot stay on the head without being held, one must hold it on the head with one’s hand, so as not to walk more than four amot, which are about two meters, without a kippa.¹
Notes (1)
- This is the reason it is permitted to go out into the public domain on Shabbat wearing a kippa. For the Sages decreed that it is forbidden to go out into the public domain with a garment that might fall off, lest after it falls he carry it four amot in the public domain. But one may go out with a kippa, because even if it falls, there is no concern that he will carry it four amot in the public domain, since it is forbidden to walk four amot without a head covering; therefore it is clear that if he is mitzva-observant, immediately after picking up the kippa he will put it on his head (SA OḤ 301:7; MB 301:153).