The Source of Livelihood:
It is related (Sefer Me’orei Ohr) that a chasid once came to Rav Yitzchok of Lyon zy”a during the years of the Communist government and cried that he had been fired from his job and only could find parnassah if he would work on Shabbos.
The Rebbe told him, “It is stated: ‘Regarding this matter you did not believe in Hashem.’ This means that one must believe that Hashem can help him in all matters. Hashem can provide a person with a livelihood in many different ways. If a person thinks he has to take a certain job to have parnassah, he does not have sufficient emunah. If one thinks Hashem can only help him ’in this matter’, meaning that he must accept a certain form of work to be helped by Him, then he does not fully believe in Hashem.”