What is the ruling on abandoning work (as a teacher) for two days or more under the pretext of going out for da'wah, and when the principal asks about the reason for absence, the answer is "going out in the path of Allah"?

Calling to Allah is among the best deeds, and its legal rulings vary depending on individuals and circumstances. Calling to Allah may be an individual obligation (wajib 'ayn) if no one else is available, or it may be a communal obligation (fard kifayah). There is no impediment to someone who is qualified engaging in da'wah, provided that taking days off work is subject to the terms of the contract, and that his absence does not result in harm to students or others, based on the Prophet's (peace be upon him) saying: "Muslims are bound by their conditions," and "There shall be no harm or reciprocating harm."