It is a jewish custom not to cut a boy's hair until their third birthday and then on their 3 year old birthday. cut their hair short leaving their peyot (sidelocks) visible. What is the reason for this custom and where does it come from?

A fascinating discussion about the Upsherin, the 3-year-old haircutting. 

Other classes mentioned:

Why Do Many Jewish Men Have Beards? https://open.spotify.com/episode/7xY7BYAGlLDyajzT2AveRv?si=pAMy3syjT5i6s9QI6gG0PA

The 13 Attributes of Mercy https://open.spotify.com/episode/2yTWzQqJattoOKsB9VfPV0?si=9XNkDhgwTy2O3PGfC52eSw

Parallel Universes https://open.spotify.com/episode/5wwVTpeGUOGtEmuuxraaCf?si=2R3YW30TQhq8oOHW6xeOtA

The Importance of Jewish Pride https://open.spotify.com/episode/0GCMjj8MruxNWKDWayMFv6?si=95GNTl9LS3CEwpeh-Cjmcw