An exposition on the merit of the remembrance of death:

He said ﷺ, "Remember often the decapitator of pleasures.' And said, 'Were cattle to know about death what you know, you would not find among them a fat one to eat.' And 'Ā'yshah said, 'O Messenger of God, will anyone else be resurrected in the company of martyrs?' He replied, Yes, one that remembers death twenty times in every day and night.' And said ﷺ, The treasure of the believer is death. And said, 'Sufficient is death as an admonisher.' Oneday, he left for the mosque, and came upon a group of people talking and laughing. He said, 'Remember death! For by the One in Whose Hand is my soul, if you knew what I know, you would laugh very little and weep a lot.' And know that death is a terrible and enormous occurrence. Remembering it induces an aversion to the abode of vanity, a curtailment of pleasure, and a preparing for it. Yes, a man who remembers it witha preoccupied heart will not show its effect on him. The way to circumvent that is to empty his heart of anything other than it, and contemplate it as if he is contemplating a journey he is preparing for, by land or by sea; for then his heart would be overcome with contemplation upon it, and preparing for it, and nothing else. Imām Muhammad bin Muhammad Abū Hāmid al-Ghazzālī in the 40th Chapter of his Ihyā Ulūm al-Dīn.