Hadith: Death will be brought forward in the shape of a black and white ram

عَنْ أَبِي سَعِيدٍ الخُدْرِيِّ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: "يُؤْتَى بِالْمَوْتِ كَهَيْئَةِ كَبْشٍ أَمْلَحَ، فَيُنَادِي مُنَادٍ: يَا أَهْلَ الجَنَّةِ، فَيَشْرَئِبُّونَ وَيَنْظُرُونَ، فَيَقُولُ: هَلْ تَعْرِفُونَ هَذَا؟ فَيَقُولُونَ: نَعَمْ، هَذَا المَوْتُ، وَكُلُّهُمْ قَدْ رَآهُ، ثُمَّ يُنَادِي: يَا أَهْلَ النَّارِ، فَيَشْرَئِبُّونَ وَيَنْظُرُونَ، فَيَقُولُ: وهَلْ تَعْرِفُونَ هَذَا؟ فَيَقُولُونَ: نَعَمْ، هَذَا المَوْتُ، وَكُلُّهُمْ قَدْ رَآهُ، فَيُذْبَحُ ثُمَّ يَقُولُ: يَا أَهْلَ الجَنَّةِ خُلُودٌ فَلاَ مَوْتَ، وَيَا أَهْلَ النَّارِ خُلُودٌ فَلاَ مَوْتَ، ثُمَّ قَرَأَ: {وَأَنْذِرْهُمْ يَوْمَ الحَسْرَةِ إِذْ قُضِيَ الأَمْرُ وَهُمْ فِي غَفْلَةٍ} [مريم: 39]، وَهَؤُلاَءِ فِي غَفْلَةٍ أَهْلُ الدُّنْيَا {وَهُمْ لاَ يُؤْمِنُونَ} [مريم: 39]".
[صحيح] - [متفق عليه]

Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported: The Prophet (may Allah’s peace and blessings be upon him) said: "Death will be brought forward in the shape of a black and white ram. Then a caller will call out: 'O people of Paradise!' Thereupon, they will stretch their necks and look carefully. The caller will say: 'Do you know this?' They will say: 'Yes, this is death.' By then all of them will have seen it. Then it will be announced again: 'O people of Hellfire!' They will stretch their necks and look carefully. The caller will say: 'Do you know this?' They will say: 'Yes, this is death.' And by then all of them will have seen it. Then it (that ram) will be slaughtered and the caller will say: 'O people of Paradise, eternity for you and no death; O people of Hellfire, eternity for you and no death.'" Then, the Prophet (may Allah’s peace and blessings be upon him) recited: {Warn them of the Day of Remorse when all matters will be decided, but they are heedless} [Surat Mariyam: 39]. And the people of the worldly life are heedless. {And they do not believe.} [Surat Mariyam: 39]
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

The Prophet (may Allah’s peace and blessings be upon him) informs in the Hadīth that death will be brought on the Day of Judgment in the form of a black and white ram. Then, a caller will call the dwellers of Paradise, and they will stretch their necks and raise their heads to look. He will say to them: Do you know this ram? They will say: Yes, this is death. All of them did see it when they died. Then, he will call the dwellers of Hellfire, and they will stretch their necks and raise their heads to look. He will ask them: Do you know this ram? They will say: Yes, this is death. They all did see it when they died. Then death will be slaughtered, after which the caller will say: O dwellers of Paradise, eternal stay in Paradise, and you will never die after your first death. O dwellers of Hellfire, eternal stay in Hellfire without death, relief, or useful living. Then, the Prophet (may Allah’s peace and blessings be upon him) recited the verse that says: {Warn them of the Day of Remorse when all matters will be decided, but they are heedless} [Surat Maryam: 39]. He interpreted the verse as referring to those people, demonstrating that they are followers of the worldly life, as the Hereafter is not an abode of heedlessness. {And they do not believe} [Surat Maryam: 39]. They lived in disbelief and heedlessness and pursued the life of this world, and so they deserved eternity in Hellfire.