أحوال الصالحين
Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: “Soon there will come a time when the best property of a Muslim will be sheep that he will take to the mountaintops and the places of rainfall so as to flee with his religion from tribulations."
عن أبي سعيد الخدري -رضي الله عنه- قالَ: قالَ رسولُ اللهِ -صلى الله عليه وسلم-: "يُوشَكُ أنْ يكونَ خيرَ مالِ المسلمِ غَنَمٌ يَتَّبعُ بها شَعَفَ الجبالِ، ومواقعَ القطرِ يَفِرُّ بدينِهِ من الفتنِ".
شرح الحديث :
The Hadīth indicates the preference of living in isolation at times of tribulation, unless a person has the ability to remove such tribulation. In this case, he would be obliged to strive to remove it, either as an individual religious duty or a collective duty (i.e. if someone undertook and competed it, it is waived from the obligation of the others) according to the situation and ability. As to the times that are free of tribulation, scholars held different opinions regarding which is better: to isolate oneself from people or to interact with them? The chosen opinion is that interaction is better for the one who believes that he would most likely not yield to temptations of committing sin. “to flee with his religion from tribulations” means to escape for fear that his religious commitment would be affected. For this reason, man was commanded to migrate from the lands of infidelity to the lands of Islam, and from countries where immorality is rampant to those where righteousness prevails. So, this should be done when people and times change.