Rambam (Hilchos Talmud Torah 3:10)Whoever decides that he will study Torah and not have a job and therefore will be financed from tzedaka – disgraces G‑d (chilulul HaShem), degrades the Torah and extinguishes the light of religion and causes evil to himself and removes his life from the World to Come. That is because it is prohibited to benefit from the words of Torah in this world. Our Sages said that whoever benefits from words of Torah takes his life from the world. Furthermore they commanded not to make Torah into a crown to be elevated in the eyes of others nor should Torah be used as a shovel to dig with. Furthermore they said to love work and to hate the rabbinate. They also said that all Torah which is not accompanied by a job will in the end be lost and will bring about sin and that in the end such a person will end up stealing from others.
Avos(2:2): It is wonderful to combine Torah study with a worldly occupation because the efforts invested in both cause sin to be forgotten. And all Torah study which is not combined with worldly occupation eventually comes to nothing and brings sin in its trail…
Berachos(35b): R’ Yishmael said that Torah study should be combined with a job. R’ Shimon Bar Yochai said that is impossible. If one ploughs, sows, reaps, threshes and winnows in the appropriate season there is no time to master Torah. In fact if one is totally devoted to serving G‑d then all his work is done for him by others… Abaye said that many have followed the advice of R’ Yishmael and have been successful while many who have followed the advice of R’ Shimon Bar Yochai have not been successful. Raba requested his students not to come to yeshiva during the months of Nissan (in order to plant) and Tishri (in order to harvest) so that they not need to worry about sustenance during the rest of the year