Our Rabbis instituted that a man should not walk four amot, a distance of about 7-8 feet, with his head uncovered. The Halacha is not specific about the type of covering that is needed. Consequently, one may wear what we call in Hebrew, a kippa or in Yiddish, a yarmulke, or a baseball cap or even a top hat as long as his head is covered. How do we understand the reasoning behind this practice?
    The source for this halacha is found in the Gemara.  Rav Huna the son of Rav Yehoshua would not walk four amot with an uncovered head. Rav Huna said, “The Shechina, God’s presence, is above my head.” Rabbi Yechiel Michel Epstein, the author of the Aruch Hashulchan, explains how this works. He writes that the head, the place of the brain, is the source for all thoughts and emotions. It is also the place that our fear of sin stems from. Just as it is not proper to enter a holy place with an uncovered head, so too, it is not proper to have an uncovered head in front of the Shechina whose place fills the entire world.  Only when a person’s head is uncovered does the brazenness of his yetzer harah attack him and bring him to sin.
    The Aruch Hashulchan brings a very interesting proof to this explanation from the Gemara in Masechet Shabbat. The Gemara tells a story about how the mother of Rav Nachman was told by astrologers that her son would be a thief. She was very careful to keep his head covered and told her son, “Cover your head so that the fear of heaven may be upon you, and ask for mercy.” Rashi comments that she was telling him to pray for mercy from God that the yetzer harah should not take hold of him. The Gemara relates that Rav Nachman didn’t know why she did all of this until one day it became clear.  He was sitting under a fruit tree that belonged to someone else when his head covering slipped off.  He lifted his eyes and saw the dates hanging from the tree.  Without thinking he grabbed one and bit into it thus becoming a thief.
    In conclusion, there is much discussion in the rabbinic literature as to whether the practice of wearing a head covering is an actual halacha or a very strong custom. The ramifications of either position are significant. However, it’s clear that covering one's head can bring a person to a higher level of fear of Heaven and potentially keep a person away from sin.