وَالَّذِينَ كَفَرُوا بَعْضُهُمْ أَوْلِيَاءُ بَعْضٍ ۚ إِلَّا تَفْعَلُوهُ تَكُن فِتْنَةٌ فِي الْأَرْضِ وَفَسَادٌ كَبِيرٌ
“Those who disbelieve—they are friends and protectors of one another (especially against you). Unless you do it also (i.e. maintain solidarity among yourselves as believers) there will be unrest on the earth and great corruption.” (Al-Anfāl 8:73)
The verse prior to the one above, “Those who have believed and emi-grated (to the home of Islam), and striven hard with their wealth and persons in God’s cause, and those who give refuge (to them) and help (them)—those (illustrious ones) are friends and protectors of one another (and can inherit from one another),” decreed that those who emigrated to Madīnah (Muhājirūn) and those who gave refuge to and helped them (Ansār) could inherit from one another although they were not relatives. As for the verse under discussion, it was decreed in it that the Muslims and unbelievers could not inherit from one another; unbelievers can inherit from unbelievers only. In interpreting this verse, God’s Messenger, upon him be peace and blessings, says: “I am distant from every Muslim who keeps living among unbelievers. Their fire does not give light.” In other words, the fire they kindle is not felt as a light despite their beliefs; as a result, the two different worlds cannot be distinguished from each other. This matter can be interpreted in the fol-lowing ways:
1. Fire has a great importance in deserts as a means of direction and warm. The hadīth above may be interpreted as an inability to distin-guish between the fire of the friend and that of the enemy.
2. If the sources of light or fireplaces of believers and unbelievers exist side by side, they cannot be differentiated from each other. The sources of light of believers and unbelievers should be separate so that each may not be deceived and confused.
3. The most important point is that if unbelievers and believers are mixed with one another, neglecting the basic differences of creed, morality, and goals, they may not be able to observe and preserve their metaphysical intensity and spiritual alertness against one another. They may be tolerant towards each other and live in peace, but belief and unbelief cannot be reconciled.
4. Another point is that according to the Islamic Law of Heritage, ikhtilāfu’d-dīn (the difference of religion) and ikhtilāfu’d-dārr (the differ-ence of worlds) prevent mutual inheritance. That is, both Muslims and the followers of other religions as well as the Muslim citizens of Islamic world and the citizens of non-Muslim countries that are at war with Muslims can-not inherit from each other. Apart from humanly relationships, if the basic principles of belief and practice and certain legal disciplines cannot be observed and preserved, we may cause corruption and disorder by the affairs and acts from which we hope improvement and reform. The greatest disturbance, abuse, and corruption are those caused by good intention and the acts done with the purpose of improvement. For the harm caused by good intentions is liable to be continuous. Once the masses are directed to this kind of conduct unconsciously, it will be very difficult for them to turn back to normality.
 Abū Dawūd, Jihād, 95; Tirmidhī, Siyar 42; Nasāī, Qasāma, 27