The permissibility of taking a wage or any form of money or reward for doing good deeds such as teaching is a subject of debate amongst scholars. Many pious scholars did not allow taking money for teaching hadeeth. However, the vast majority of the jurists allowed it. The origin of this issue is connected to the statement of the Prophet,
“The most worthy recompense you can take is for teaching the Qur’aan.” (Bukhaary 5737)
Therefore, if it is allowed to take it for teaching the Qur’aan, taking it for other subjects is a logical conclusion. Some scholars refuse to take money as wages for teaching Islamic studies out of piety but do take money for teaching non-Islamic subjects. Some would stipulate that they would teach the Alfiyyah of ibn Maalik and for every stanza they would receive one Dirham. Some would stipulate teaching history and the like. This is an act of piety although the basis of taking money is permissible. However, the situation should not be that a scholar or student refuses to do such-and-such except in return for such-and-such. It was said to Imaam Ahmad (may Allaah’s Mercy be upon him), ‘I will not lead you for the Ramadhaan prayers except for such-and-such amount.’ Ahmad replied, “This is a bad man! No one should pray behind him.” In any case, taking a wage for teaching as a source of livelihood while having the intention to benefit the Muslims and benefit those around him is not a problem. It is allowed. How can someone be sincere? Yes, they can be so despite taking a wage, for this does not negate sincerity. Yes, not taking a wage is closer to pure sincerity, but despite this one can be even more insincere than taking a wage especially when it is made known that he is doing it for free. In such a case, a person taking a wage is more sincere than one not doing so. Hence, taking a wage does not negate sincerity. If a person is negligent of observing his hours at work, like the questioner is asking, ‘Is it enough for me to deduct from my wages what I think is fair to recompense my negligence in the number of hours at work?,’ the answer is a person should not be negligent. However, if this occurs unintentionally and he were to take a portion of his wage which he believes reflects the time he has missed, then Allaah-willing, he has been absolved of his responsibility, and Allaah knows best.