Sahih Bukhari Volume 4, Book 58, Hadith 3173

حَدَّثَنى مُحَمَّدٌ، أَخْبَرَنَا وَكِيعٌ، عَنِ الأَعْمَشِ، عَنْ إِبْرَاهِيمَ التَّيْمِيِّ، عَنْ أَبِيهِ، قَالَ خَطَبَنَا عَلِيٌّ فَقَالَ مَا عِنْدَنَا كِتَابٌ نَقْرَؤُهُ إِلاَّ كِتَابُ اللَّهِ، وَمَا فِي هَذِهِ الصَّحِيفَةِ فَقَالَ فِيهَا الْجِرَاحَاتُ وَأَسْنَانُ الإِبِلِ، وَالْمَدِينَةُ حَرَمٌ مَا بَيْنَ عَيْرٍ إِلَى كَذَا، فَمَنْ أَحْدَثَ فِيهَا حَدَثًا أَوْ آوَى فِيهَا مُحْدِثًا، فَعَلَيْهِ لَعْنَةُ اللَّهِ وَالْمَلاَئِكَةِ وَالنَّاسِ أَجْمَعِينَ، لاَ يُقْبَلُ مِنْهُ صَرْفٌ وَلاَ عَدْلٌ، وَمَنْ تَوَلَّى غَيْرَ مَوَالِيهِ فَعَلَيْهِ مِثْلُ ذَلِكَ، وَذِمَّةُ الْمُسْلِمِينَ وَاحِدَةٌ، فَمَنْ أَخْفَرَ مُسْلِمًا فَعَلَيْهِ مِثْلُ ذَلِكَ‏

Narrated By Ibrahim At-Tamimi's father : 'Ali delivered a sermon saying, "We have no book to read except the Book of Allah and what is written in this paper which contains verdicts regarding (retaliation for) wounds, the ages of the camels (given as Zakat or as blood money) and the fact that Medina is a sanctuary in between Air mountain to so-and-so (mountain). So, whoever innovates in it an heresy or commits a sin or gives shelter in it, to such an innovator will incur the Curse of Allah, the angels and all the people, and none of his compulsory or optional good deeds of worship will be accepted. And whoever (freed slave) takes as his master (i.e. befriends) other than his real masters will incur the same (Curse). And the asylum granted by any Muslim is to be secured by all the other Muslims, and whoever betrays a Muslim in this respect will incur the same (Curse)."