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] - [صحيح البخاري: 4730]

Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported: The Messenger of Allah (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. 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. 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 will be slaughtered, and the caller will say: 'O people of Paradise, eternity and no death; O people of Hellfire, eternity 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 this 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) points out that death will be brought on the Day of Judgment in the shape of a sheep that is black and white in color. Then, it will be called out: O people of Paradise! They will stretch their necks, raise their heads, and look. He will say to them: Do you know this? They will reply: Yes, this is death. All of them will have seen and known it. Then, the caller will call out: O people of Hellfire! They will stretch their necks, raise their heads, and look. He will say: Do you know this? They will reply: Yes, this is death. All of them will have seen it. Then, it will be slaughtered, and the caller will say: O people of Paradise, eternity, and no death; O people of Hellfire, eternity, and no death. This will add to the bliss of the believers and the punishment of the disbelievers. 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.} On the Day of Judgment, the people of Paradise will be separated from the people of Hellfire, and each will enter the place where they will stay forever. So, the wrongdoer will feel sorrowful and regretful that he did not do good, and the one who fell short in doing good will regret that he did not do better.