Musar על אבות 2:2

The seventh thought which leads to rejoicing is that he should know that the Creator, Blessed is He, created man for many labors and provided food for him to obtain through much exertion and work and that if all these things like food and clothes were prepared for man without any trouble at all on his part there would be a number of commandments that would not exist — for instance Charity — laws prohibiting robbery, theft, covetousness, and many similar commandments. Then too, if all were provided, man would have no need to trust in God. And for this reason, Hezekiah the King of Judea hid the Book of Healings (Berakoth 10b) in order that the sick person should trust in God, may He be Exalted, and not merely in drugs. Moreover, if a man were freed from the necessity of work and did not have to trouble himself about his sustenance, he would kick out against all restraint and pursue wrongdoing as it is written : "When Jeshurun prospered, he kicked" (Deut. 32:15). And our Sages said : "The study of the Torah is good when combined with making a living, for the exertion necessary for both activities causes one to forget all thought of sinning" (Aboth 2:2).