What is the religious ruling regarding someone who sees nightmares and terrifying dreams, fears death, finds difficulty in eating, sleeping, and studying, and hears the sound of the Adhan upon waking up at night, all of this occurring after the death of a close relative?

Constantly remembering death is a religious requirement, as stated in the Hadith: "Remember often the destroyer of pleasures." He who remembers death frequently is honored with three things: hastening repentance, contentment of heart, and diligence in worship. And he who forgets it is punished with three: procrastination in repentance, lack of contentment with sufficiency, and laziness in worship. Remembering death must be a motivator for performing acts of obedience and abandoning sins, not a cause for despair and hopelessness. To get rid of disturbing dreams and nightmares, it is recommended to frequently remember Allah at all times, to maintain the morning, evening, and sleep remembrances (adhkar), to be keen on sleeping in a state of purity, and to increase supplication for repelling the whispers of Satan.