Abu Saeed Khudri reported,

I attended a funeral with the Messenger of Allah ﷺ, and the Messenger of Allah ﷺ said, "People, this community will be tested in their graves. When a person is buried and his companions disperse from him, an angel comes to him with a hammer in his hand and sits him up.The angel asks, 'What do you say about this man?'If he is a believer, he says, 'I bear witness that there is no god but Allah and that Muhammad is His servant and messenger.'The angel says, 'You have spoken the truth.' Then a door to the Fire is opened for him, and the angel says, 'This would have been your dwelling had you disbelieved in your Lord. But since you believed, this is your dwelling.' Then a door to Paradise is opened for him. He wants to rise toward it, but the angel says to him, 'Stay still,' and his grave is widened for him.But if he is a disbeliever or a hypocrite, the angel says to him, 'What do you say about this man?'He says, 'I do not know. I heard people saying something.'The angel says, 'You did not know, you did not recite, you did not follow guidance.' Then a door to Paradise is opened for him, and the angel says, 'This would have been your dwelling had you believed in your Lord. But since you disbelieved in Him, Allah has exchanged it for this.' Then a door to the Fire is opened for him. Then the angel strikes him a blow with the hammer that all of Allah's creation hears except for the two species of jinn and humans, except for the two species of jinn and humans."Some of the people said, "Messenger of Allah, no one would have an angel standing over him with a hammer in his hand without being terrified at that moment."The Messenger of Allah ﷺ said, "Allah keeps firm those who believe with the firm word" [Ibrahim 14:27].

عن أبي سعيد الخدري قال

شهدت مع رسول الله ﷺ جنازة فقال رسول الله ﷺ: يا أيها الناس إن هذه الأمة تبتلى في قبورها، فإذا الإنسان دفن، فتفرق عنه أصحابه، جاءه ملك في يده مطراق، فأقعده، قال: ما تقول في هذا الرجل؟ فإن كان مؤمنا قال: أشهد أن لا إله إلا الله وأن محمدا عبده ورسوله، فيقول: صدقت، ثم يفتح له باب إلى النار، فيقول: هذا كان منزلك لو كفرت بربك، فأما إذ آمنت فهذا منزلك، فيفتح له باب إلى الجنة، فيريد أن ينهض إليه، فيقول له: اسكن، ويفسح له في قبره، وإن كان كافرا أو منافقا يقول له: ما تقول في هذا الرجل؟ فيقول: لا أدري، سمعت الناس يقولون شيئا، فيقول: لا دريت ولا تليت ولا اهتديت، ثم يفتح له باب إلى الجنة فيقول: هذا منزلك لو آمنت بربك، فأما إذا كفرت به، فإن الله عز وجل أبدلك به هذا، ويفتح له باب إلى النار، ثم يقمعه قمعة بالمطراق يسمعها خلق الله كلهم غير الثقلين غير الثقلين، فقال بعض القوم: يا رسول الله، ما أحد يقوم عليه ملك في يده مطراق إلا هيل عند ذلك، فقال رسول الله ﷺ: {يثبت الله الذين آمنوا بالقول الثابت} [إبراهيم: ٢٧].