The Messenger of Allah ﷺ said, "Prompt your dying ones to say, 'There is no god but Allah.'"
قال رسول الله ﷺ: لقنوا موتاكم لا إله إلا الله.
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Muslim narrated it in the Book of Funerals (916) through several routes from Umara bin Ghaziya, who said, Yahya bin Umara narrated to us, saying, I heard Abu Saeed Khudri, and he related the hadith.His saying, "Prompt your dying ones," refers to one whom death has approached, not one who has already died. The purpose of this prompting is that his last words should be "There is no god but Allah," as will come in the chapter after this one. It has likewise been said that if he says it once, it should not be repeated to him unless he speaks other words afterward.