What is the ruling regarding the salary of an Imam who appoints someone else to lead the prayer, and then that appointee also becomes absent, and how can he expiate for past salaries if they were unlawful?

One who has been appointed to lead prayers in a mosque for a salary is obligated to fully commit to leading the people in prayer. He should not be absent except for a necessity or a need; otherwise, he is sinful. The salary he receives for his unauthorized absence is not permissible for him to keep; rather, it must be returned or spent on general Muslim welfare, or given to the poor and the needy. Appointing someone else to lead does not absolve him of responsibility nor does it make the salary permissible, unless the responsible authority has given permission for that. What then, if the appointed deputy also fails to attend?