Is money earned from work that causes one to miss congregational prayer – while performing the prayer individually – unlawful, by analogy with selling during Friday prayer? And is enrolling in study courses that cause one to miss congregational prayer unlawful?

There is no blame upon an employee, such as a guard or a teacher, whose work prevents him from attending congregational prayers, especially if the employer does not permit him, or if leaving his post would cause harm to his work or his finances. It is recommended for him to pray with the students during break time if possible, and to invite them to prayer and to congregational prayer. The money he earns is lawful, and it is not related to his missing congregational prayer if his absence is due to a valid excuse. One must be diligent in learning the rulings of the Sacred Law while being wary of obsessive doubts (waswas (definition)).