Hadith: Madīnah is a sanctuary from ‘Ayr to Thawr (mountains). Whoever innovates something new (in religion) or shelters an innovator in it will incur the curse of Allah, the angels, and all the people, and Allah will accept from him neither an obligatory nor a supererogatory prayer on the Day of Resurrection

عن يزيد بن شريك بن طارق، قال: رأيت عليًّا رضي الله عنه على المنبر يخطب، فسمعته يقول: لا والله ما عندنا من كتاب نقرؤه: إلا كتاب الله، وما في هذه الصَّحِيفَةِ، فنشرها؛ فإذا فيها: أَسْنَانُ الإبل، وأشياء من الجِرَاحَاتِ. وفيها: قال رسول الله صلى الله عليه وسلم : «المدينة حَرَمٌ ما بين عَيْرٍ إلى ثَوْرٍ، فمن أحدث فيها حَدَثًا، أو آوى مُحْدِثًا؛ فعليه لعنة الله والملائكة والناس أجمعين، لا يقبل الله منه يوم القيامة صَرْفًا ولا عَدْلًا. ذِمَّةُ المسلمين واحدة، يسعى بها أَدْنَاهُم، فمن أَخْفَرَ مسلما، فعليه لعنة الله والملائكة والناس أجمعين، لا يقبل الله منه يوم القيامة صَرْفًا ولا عَدْلًا. ومن ادعى إلى غير أبيه، أو انتمى إلى غير مواليه، فعليه لعنة الله والملائكة والناس أجمعين؛ لا يقبل الله منه يوم القيامة صَرْفًا ولا عَدْلًا».
[صحيح] - [متفق عليه]

Yazīd ibn Sharīk ibn Tāriq reported: I saw ‘Ali (may Allah be pleased with him) delivering a speech from the pulpit, and I heard him say: "By Allah! We have no book to read except the Book of Allah and what is written in this scroll." He unrolled the scroll, and it showed a list of the types of camels to be given as blood-money and contained other legal matters relating to the killing of game in the sanctuary of Makkah and the expiation for it. In it was also written: "The Messenger of Allah (may Allah's peace and blessings be upon him) said: 'Madīnah is a sanctuary from ‘Ayr to Thawr (mountains). Whoever innovates something new (in religion) or shelters an innovator in it will incur the curse of Allah, the angels, and all the people, and Allah will accept from him neither an obligatory nor a supererogatory prayer on the Day of Resurrection. A pledge of protection granted by any Muslim, even of the lowest status is the same and should be honored by all Muslims. Whoever betrays a Muslim in this respect will incur the curse of Allah, the angels, and all the people, and Allah will accept from him neither an obligatory nor a supererogatory prayer on the Day of Resurrection. Whoever attributes his fatherhood to someone other than his (real) father or takes as his master someone other than his (real) master will incur the curse of Allah, the angels, and all the people, and Allah will accept from him neither an obligatory nor a supererogatory prayer on the Day of Resurrection.'"
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

While delivering a speech from the pulpit, ‘Ali (may Allah be pleased with him) said: “By Allah! We have no book to read except the Book of Allah and what is written in this scroll.” As he unrolled it, it showed a list of the types of camels to be given as blood-money and it contained other legal matters relating to the killing of game in the sanctuary of Makkah and the expiation for it. It also included the Prophet's statement declaring Madīnah as inviolable as Makkah, from Mount ‘Ayr to Mount Thawr. Whoever introduces a religious innovation in it, causes any harm to Muslims, or shelters an innovator will incur the curse of Allah, which means deprivation of His mercy, and the angels and all people will ask Allah to expel him from His mercy. Then, on the Day of Judgment, Allah, the Almighty, will not accept any prayer (obligatory or supererogatory), repentance, or ransom from him. Moreover, the protection given by any Muslim to a non-Muslim is valid, as long as it conforms to the relevant conditions. Once in place, it is prohibited to violate it. If anyone does so, he will be subject to the curse of Allah, which means he will be deprived of His mercy, and the angels and all people will ask the Almighty Lord to expel him from His mercy. Then, on the Day of Judgment, Allah, the Almighty, will not accept any prayer, obligatory or supererogatory, repentance, or ransom from him. If someone attributes himself to someone other than his real father or if a freed slave attributes himself to someone other than his master, he will incur the curse of Allah, the Almighty, which means deprivation of His mercy, and the angels and all people will ask Allah to expel him from His mercy. Then, on the Day of Judgment, Allah, the Almighty, will not accept any prayer (obligatory or supererogatory), repentance, or ransom from him. This is because these actions involve ingratitude and cause a loss of the rights to inheritance, allegiance, blood-money, and so on, and sever the ties of kinship.