There is a special mitzvah that applies to newly married couples. The Torah (Deut. 24:5) tells us that when people are called up to the army, newly married men are exempt for the first year of their marriages:
כי יקח איש אשה חדשה לא יצא בצבא ולא יעבר עליו לכל דבר נקי יהיה לביתו שנה אחת ושמח את אשתו אשר לקח.
When a man has taken a new wife, he shall not go out to war nor be charged with anything; he shall be free at home one year, and bring happiness to his wife whom he has taken.It is significant that the Torah uses repetitive language in this verse in that it says that a groom need not go to war nor "be charged with anything." What does this second phrase imply? The Gemara (Sotah 44a) understands this as meaning that a groom does not leave his wife for anything. The question is whether this "anything" means battle-related duties, i.e. national service, or literally anything.
Click here to read moreRashi (Deut. 24:5) writes that it refers specifically to national service. However, the Sefer Ha-Chinukh (no. 581) explains at length that, in his view, a groom in his first year of marriage may not leave his wife for an extended period of time except for the purposes of a mitzvah (including an obligatory war) or -- seriously -- to have fun with his friends. This position of the Chinukh, as well as a mistranslation of the Rambam's Arabic Sefer Ha-Mitzvos (lavin 311), has led some authorities to rule that a groom may not leave his wife for a few days within the first year of marriage. In particular, the Chokhmas Adam (129:19) is strict about this. Others, such as the Minchas Chinukh (581:2), deny that this mitzvah applies to anything other than war.
The Chasam Sofer (Responsa, EH vol. 2 no. 155) was asked by a man whether, in his first year of marriage, he may leave for a business trip. He was an importer and needed to buy his wares in a distant land in order to have merchandise to sell. The responsum does not specify but given that this man was in his first year of marriage and there is no mention of any children he needs to feed, it is probably safe to assume that we are dealing with only a question of a husband supporting himself and his wife.
The Chasam Sofer responded that the Sefer Ha-Chinukh allows travel for a mitzvah. Since earning a living is a mitzvah, the man may travel for business.
Let me repeat, the Chasam Sofer ruled in an halakhic context that earning a living is a mitzvah.
This should not be surprising. It is, after all, one of the ten commandments (Ex. 20:8): "Six days you shall work..." The Avos De-Rabbi Nassan (version 2 ch. 21) derives from here an obligation to work.* It doesn't get more authoritative than the ten commandments.
* Although see the responsum of the Chakham Tzvi (no. 83) in which he states that this verse only implies an option and not an obligation. I'm not sure what he does with the Avos De-Rabbi Nassan. For a lengthy discussion of the implication of this biblical phrase, see Torah Shelemah vol. 16 on Ex. ch. 20 no. 240; addenda no. 14.