What is the ruling on receiving a salary during a one-month verbal leave from work, knowing that it is a legally deserved leave? If the salary is not permissible, is it permissible to use part of it to cover the costs of virus tests due to work circumstances and then donate the rest?

If your manager is authorized by the employer to grant you paid leave without formal registration, then there is no harm in you taking it. However, if he does this on his own initiative and it is not permitted by the employer, then it is impermissible due to the breach of contract and deception involved, and you must return the salary you received unjustly.