Hadith: We were talking about the Farewell Hajj, when the Prophet (may Allah's peace and blessings be upon him) was with us. We did not know what the Farewell Hajj signified

عن ابن عمر رضي الله عنهما ، قال: كنا نتحدث عن حَجَّةِ الوداع، والنبي صلى الله عليه وسلم بين أظهرنا، ولا ندري ما حَجَّةُ الوداع حتى حمد اللهَ رسولُ الله صلى الله عليه وسلم وأثنى عليه، ثم ذكر المَسِيحَ الدَّجَالَ، فأَطْنَبَ في ذكره، وقال: «ما بعث الله من نبي إلا أَنْذَرَهُ أُمَّتَهُ، أنذره نوح والنبيون من بعده، وإنه إن يخرج فيكم فما خَفِيَ عليكم من شأنه فليس يخفى عليكم، إن ربكم ليس بأَعْوَرَ، وإنه أَعْوَرُ عَيْنِ اليُمْنَى، كأنَّ عينه عِنَبَةٌ طَافِيَةٌ. ألا إن الله حرم عليكم دماءكم وأموالكم كحُرْمَةِ يومكم هذا، في بلدكم هذا، في شهركم هذا، ألا هل بلغت؟» قالوا: نعم، قال: «اللهم اشهد» ثلاثا «ويلكم - أو ويحكم -، انظروا: لا ترجعوا بعدي كُفَّارًا يضرب بعضكم رِقَابَ بعض».
[صحيح] - [متفق عليه]

Ibn ‘Umar (may Allah be pleased with him) reported: We were talking about the Farewell Hajj, when the Prophet (may Allah's peace and blessings be upon him) was with us. We did not know what the Farewell Hajj signified. The Messenger of Allah (may Allah's peace and blessings be upon him) praised Allah and then mentioned the Anti-Christ, describing him extensively, saying: "Allah did not send any prophet but that prophet warned his nation of the Anti-Christ. Nūh and the prophets following him warned [their people] of him. He will appear among you and some of his qualities will be hidden from you, but it should not be hidden from you that your Lord is not one-eyed. He (the Anti-Christ) is blind in the right eye and it looks like a bulging grape. Allah has certainly made your blood and your property inviolable, like the sanctity of this day of yours, in this town of yours, in this month of yours." The Prophet (may Allah's peace and blessings be upon him) added: ''Have I conveyed [Allah's Message to you]?" They replied: 'Yes.' The Prophet (may Allah's peace and blessings be upon him) said three times: "O Allah, bear witness [to that]." The Prophet (may Allah's peace and blessings be upon him) added: "Woe to you!" (or) "May Allah be merciful to you! Do not become disbelievers after me, cutting the necks of one another."
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

Ibn ‘Umar (may Allah be pleased with him) reported: We would say when the Prophet (may Allah's peace and blessings be upon him) was alive: "What is the Farewell Hajj? We did not know what it meant." The Farewell Hajj was the Hajj that the Prophet (may Allah's peace and blessings be upon him) performed in the tenth year after Hijrah, when he bid farewell to the Muslims. He mentioned the Anti-Christ and warned extensively of him. Then, he mentioned that all the prophets had warned their followers of the Anti-Christ, raising their awareness of him by giving many descriptions of him. The Prophet (may Allah's peace and blessings be upon him) said that the Anti-Christ should not be unknown, because Allah is not one-eyed, whereas the Anti-Christ is and his right eye is like a protruding grape. Then the Prophet (may Allah's peace and blessings be upon him) said that Allah forbade the shedding of blood and the seizing of property without a right, in the same way He had made the Day of An-Nahr, Makkah, and the month of Dhu al-Hijjah inviolable. The Prophet (may Allah's peace and blessings be upon him) then asked the Companions if he had conveyed the message that he had been ordered to communicate, and they said that he had. Upon that, he asked Allah, the Almighty, three times to witness their testimony. he then ordered them to not become disbelievers, killing each other, after his death.