Hadith: Time has completed its cycle and has returned to its state when Allah created the heavens and the earth. A year consists of twelve months, of which four are sacred; three of them are consecutive: Dhu al-Qi‘dah, Dhu al-Hijjah, Muharram, and Rajab of Mudar

عن أبي بكرة -ضي الله عنه- مرفوعاً: «إِنَّ الزمانَ قَدِ اسْتَدَارَ كَهَيْئَتِهِ يَوْمَ خَلَقَ اللهُ السَّمَاوَاتِ والأَرْضَ: السنةُ اثنا عَشَرَ شَهْرًا، منها أربعةٌ حُرُمٌ: ثلاثٌ مُتَوَالِيَاتٌ: ذُو القَعْدَةِ، وذُو الحَجَّةِ، والمحرمُ، ورَجَبُ مُضَرَ الذي بين جُمَادَى وشَعْبَانَ، أَيُّ شَهْرٍ هَذَا؟» قلنا: اللهُ ورسولُهُ أَعْلَمُ، فسكتَ حتى ظننا أنه سَيُسَمِّيهِ بغير اسمه، قال: «أَلَيْسَ ذَا الحَجَّةِ؟» قُلْنَا: بَلَى. قال: «فأَيُّ بَلَدٍ هَذَا؟» قلنا: اللهُ ورسولُهُ أَعْلَمُ، فسكتَ حتى ظننا أنه سُيَسَمِّيهِ بغير اسمه. قال: «أَلَيْسَ البَلْدَةَ؟» قلنا: بلى. قال: «فأَيُّ يَوْمٍ هَذَا؟» قُلْنَا: اللهُ ورسولُهُ أَعْلَمُ، فسكتَ حتى ظَنَنَّا أنه سيسميه بغير اسمه. قال: «أَلَيْسَ يَوْمَ النَّحْرِ؟» قلنا: بَلَى. قال: «فَإِّنَّ دِمَاءَكُمْ وأَمْوَالَكُمْ وأَعْرَاضَكُمْ عَلَيْكُمْ حَرَامٌ، كَحُرْمَةِ يَوْمِكُمْ هَذَا في بَلَدِكُمْ هَذَا فِي شَهْرِكُمْ هَذَا، وَسَتَلْقَونَ رَبَّكُمْ فَيَسْأَلُكُمْ عَنْ أَعْمَالِكُمْ، أَلَا فَلَا تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُم رِقَابَ بَعْضٍ، أَلَا لِيُبَلِّغِ الشَّاهِدُ الغَائِبَ، فَلَعَلَّ بَعْضَ مَنْ يَبْلُغُهُ أَنْ يكونَ أَوْعَى لَهُ مِنْ بَعْضِ مَنْ سَمِعَهُ»، ثُمَّ قال: «أَلَا هَلْ بَلَّغْتُ، أَلَا هَلْ بَلَّغْتُ؟» قلنا: نعم. قال: «اللَّهُمَّ اشْهَدْ».
[صحيح] - [متفق عليه]

Abu Bakrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "Time has completed its cycle and has returned to its state when Allah created the heavens and the earth. The year consists of twelve months, of which four are sacred; three of them are consecutive: Dhu al-Qi‘dah, Dhu al-Hijjah, Muharram, and Rajab of Mudar which comes between the months of Jumāda and Sha‘bān. Which month is this?" We said: "Allah and His Messenger know best." He remained silent for some time until we thought he was going to name it by something other than its current name. He then said: "Is this not the month of Dhu al-Hijjah?" We said: "Indeed, it is." He then said: "Which city is this?" To which we said: "Allah and His Messenger know best." He then remained silent for some time until we thought he was going to name it by something other than its current name. He then said: "Is this not Al-Baldah (meaning Makkah)?" We said: "Indeed, it is." He then said: "What day is this?" We replied saying: "Allah and His Messenger know best." He then remained silent for some time until we thought he was going to name it by something other than its current name. He said: "Is this not the Day of An-Nahr (10th of Dhu al-Hijjah)?" We said: "Indeed, it is." Thereupon he said: "Indeed, your blood, your property and your honor are inviolable to one another just as the inviolability of this day of yours, in this city of yours, in this month of yours. And you will soon meet your Lord, and He will ask you about your deeds. So, do not return to disbelief after my death, striking each other's necks. Let those who are present here convey my statements to those who are not present, for perhaps someone to whom my words are conveyed will understand them better than someone who listened to them." Then he said: "Behold! Have I delivered (the message) to you? Behold! Have I delivered (the message) to you?" We answered saying: "Indeed, you have." He said: "O Allah, bear witness to this!"
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) delivered a sermon on the Day of An-Nahr, during the Farewell Hajj. He informed his Companions(may Allah be pleased with him) that at that point of time in the year, the Nasī’ (postponement of the sacred months people used to do in pre-Islamic Arabia) became in accordance with what Allah has legislated with regard to the sacred months. That is because the people of Jāhiliyyah (pre-Islamic times) had altered the order Allah had set for the sacred months. They would deem sacred months to be not sacred, and turned months that are not sacred to be sacred, in order to fight and oppress each other whenever they so willed. The Prophet (may Allah's peace and blessings be upon him) then explained that the year consists of twelve months, which are: Muharram, Safar, Rabī‘ al-Awwal, Rabī‘ Ath-Thāni, Jumāda al-’Ūla, Jumāda Ath-Thāniyah, Rajab, Sha‘bān, Ramadan, Shawwāl, Dhu al-Qi‘dah, and Dhu al-Hijjah. These are the twelve months of the year that Allah has made for His servants since the creation of the heavens and the earth. The Messenger of Allah (may Allah’s peace and blessings be upon him) then explained that four of these months are sacred, and that three of these four months are consecutive and one is separate. The three consecutive months are: Dhu al-Qi‘dah, Dhu al-Hijjah, and Muharram. Allah has made these months sacred, meaning that fighting is not permissible in them, and no tribe is allowed to attack another therein. The reason for this is that these are the months in which people travel to Makkah to perform Hajj. It is part of Allah’s divine wisdom that He made these months sacred so that no fighting occurs during the months of Hajj. The Messenger of Allah (may Allah's peace and blessings be upon him) then said: "and Rajab of Mudar (tribe) that comes between Jumāda and Sha‘bān." This is the fourth of the sacred months, and the people before Islam would perform ‘Umrah exclusively in this month, and then perform Hajj during the other three sacred months. This month then became sacred as well, just as the other three were. The Messenger of Allah (may Allah’s peace and blessings be upon him) then asked them about what month they were in, what city they were in, and what day it was. He asked them this in order to alert them and evoke their attention, because what he was going to say next was very important. When he asked them what month they were in, they said "Allah and His Messenger know best". They said this because they did not think the Prophet would ask a question with such a readily known answer, so they assumed he would say something they did not know. They therefore answered saying "Allah and His Messenger know best". This reply reflects their good manners. He then remained silent, because people pay attention to the speaker when he pauses. Abu Bakrah said that his silence was so long that they thought he was going to give it a name other than its known name. He then said: "Is it not Dhu al-Hijjah?" They answered: "Indeed, it is!" He then asked what city they were in. They answered saying that Allah and His Messenger knew best, even though they knew it was Makkah. However, out of respect to the Messenger of Allah, they gave this answer. They did not say to him that this was something already known, or say: "This is well known, O Messenger of Allah. Why are you asking us about it?" Rather, they answered politely and in a manner befitting the situation. The Messenger of Allah then remained silent, to the point that they thought he would give it another name. He then said: "Is it not Al-Baldah?" Al-Baldah is one of the names of Makkah. They said: "Indeed, it is!" He then asked: "What day is this." They answered: "Allah and His Messenger know best," just as they did previously. He said: "Is it not the Day of An-Nahr?" They said: "Indeed, it is, O Messenger of Allah," They said this knowing that it was the sacred month of Dhu al-Hijjah, in the sacred city of Makkah, on the sacred Day of An-Nahr, meaning that they were all held as sacred. He then said: "Verily, your blood, property and honor are sacred (inviolable) to you like the sacredness of this day of yours, in this city of yours, in this month of yours." He emphasized the sacredness of these three things: Blood, property and honor. These three are sacred in the sight of Allah. The word blood includes human life and what is subordinate to it (human body), property includes both large and small amounts, and honor includes illicit sexual intercourse, sodomy and false accusations of immorality, and it may also include backbiting, insulting and cursing. These three things are unlawful for a Muslim to violate with regard to his Muslim brother. He then said: "Do not return to disbelief after my death, striking the necks of one another." If Muslims started to kill each other, they become disbelievers, because a Muslim does not deem the blood of another Muslim lawful; only a non-Muslim does this. He then ordered those who witnessed his sermon to transmit it to those who were absent, and said that perhaps someone to whom the content of the sermon is conveyed might have better understanding of it than the one who heard it from him directly. This was a command to the Companions who attended the sermon, as well as to all those who hear this Hadīth until the Day of Judgment. The Messenger of Allah (may Allah’s peace and blessings be upon him) then said: "Behold, have I delivered the message? Have I delivered the message?" He was asking his Companions that question and they answered: "Indeed, you have." He then said: "O Allah, bear witness to this!"