Sahih Bukhari Volume 1, Book 3, Hadith 67

حَدَّثَنَا مُسَدَّدٌ، قَالَ حَدَّثَنَا بِشْرٌ، قَالَ حَدَّثَنَا ابْنُ عَوْنٍ، عَنِ ابْنِ سِيرِينَ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي بَكْرَةَ، عَنْ أَبِيهِ، ذَكَرَ النَّبِيَّ صلى الله عليه وسلم قَعَدَ عَلَى بَعِيرِهِ، وَأَمْسَكَ إِنْسَانٌ بِخِطَامِهِ ـ أَوْ بِزِمَامِهِ ـ قَالَ ‏"‏ أَىُّ يَوْمٍ هَذَا ‏"‏‏.‏ فَسَكَتْنَا حَتَّى ظَنَنَّا أَنَّهُ سَيُسَمِّيهِ سِوَى اسْمِهِ‏.‏ قَالَ ‏"‏ أَلَيْسَ يَوْمَ النَّحْرِ ‏"‏‏.‏ قُلْنَا بَلَى‏.‏ قَالَ ‏"‏ فَأَىُّ شَهْرٍ هَذَا ‏"‏‏.‏ فَسَكَتْنَا حَتَّى ظَنَنَّا أَنَّهُ سَيُسَمِّيهِ بِغَيْرِ اسْمِهِ‏.‏ فَقَالَ ‏"‏ أَلَيْسَ بِذِي الْحِجَّةِ ‏"‏‏.‏ قُلْنَا بَلَى‏.‏ قَالَ ‏"‏ فَإِنَّ دِمَاءَكُمْ وَأَمْوَالَكُمْ وَأَعْرَاضَكُمْ بَيْنَكُمْ حَرَامٌ كَحُرْمَةِ يَوْمِكُمْ هَذَا، فِي شَهْرِكُمْ هَذَا، فِي بَلَدِكُمْ هَذَا‏.‏ لِيُبَلِّغِ الشَّاهِدُ الْغَائِبَ، فَإِنَّ الشَّاهِدَ عَسَى أَنْ يُبَلِّغَ مَنْ هُوَ أَوْعَى لَهُ مِنْهُ"

Narrated By 'Abdur Rahman bin Abi Bakra's father : Once the Prophet was riding his camel and a man was holding its rein. The Prophet asked, "What is the day today?" We kept quiet, thinking that he might give that day another name. He said, "Isn't it the day of Nahr (slaughtering of the animals of sacrifice)" We replied, "Yes." He further asked, "Which month is this?" We again kept quiet, thinking that he might give it another name. Then he said, "Isn't it the month of Dhul-Hijja?" We replied, "Yes." He said, "Verily! Your blood, property and honour are sacred to one another (i.e. Muslims) like the sanctity of this day of yours, in this month of yours and in this city of yours. It is incumbent upon those who are present to inform those who are absent because those who are absent might comprehend (what I have said) better than the present audience."