While passing through a marketplace, Rabbi Kehot of Veritch, a disciple of Rabbi Israel Baal Shem Tov, overheard a conversation between two horse dealers.
“I was thinking,” said one to the other. “What does the psalmist mean when he says, ‘Do not be as a horse, or a mule, without understanding, their mouths stopped with bit and bridle’? Well, when you put a bit in a horse’s mouth, he thinks that you are giving him something to practice his chewing on. Don’t be like a horse, King David is saying. When your Heavenly Master sends something your way, understand that it is more than something to chew on…”
Rabbi Kehot related this exchange to his teacher. The Baal Shem Tov was greatly excited by the horse dealer’s insight, and was inspired to a state of d’veikut (meditative attachment to G-d). In his ecstasy, the Baal Shem Tov began to sing a melody. This is the melody to which the rebbes of Chabad would pray on the first night of Rosh Hashanah.
Adapted from the teachings of the Rebbe by Yanki Tauber
 Psalms 32:9.