After having learned Torah and become a rabbi, the Tanah says that in addition to Torah learning, one must have a craft from which to earn a livelihood. When one begins studying, one should not work for a living, as Torah scholars have decreed, and study out of effort, as HaZa”L said, “The righteous first suffer and end up at peace”. Once a person has already studied Torah, the person should seek a livelihood, as it says, “And all study of the Torah in the absence of a worldly occupation comes to nothing in the end and leads to sin”… It leads others to sin, for all things are visible, and those who see a great Torah scholar who nevertheless has no income, will be fearful and no longer wish to study.