The Gemara (Rosh Hashanah 26B) states: “The Rabbanan didn’t know the meaning of the verse (Tehillim 55:23): “Throw your burden (yehavcha) on Hashem, and He will sustain you.” (They didn’t know the meaning of the word ‘yehavcha’.) Rabba bar bar Chana said: One day, I was walking on the road, accompanied by an Arab merchant. I was carrying my bundle on my shoulder and he said to me: Take yehavcha (your burden) and throw it on my camel. I then understood that ‘yehavcha’ means ‘a burden’.” Thus, the pasuk is saying that Hashem says to throw your burden of worry upon Him and trust in Him to carry it for you.
The Kotzker Rebbe zy”a explains this Gemara to mean that the Rabbanim didn’t know the extent of bitachon one must have until Rabba bar bar Chana told them this story, in which he didn’t even ask for help but the merchant offered it on his own. They learned from this that one doesn’t have to look for a means of help. If he has bitachon, Hashem will send the means. This is the type of bitachon one must have regarding his parnassah.
