الفرار من الطاعون
Guidance not to enter a land where plague has broken out, and not to flee a land you are already in once it has broken out there — an early quarantine principle.
إِذَا سَمِعْتُمْ بِهِ بِأَرْضٍ فَلَا تَقْدَمُوا عَلَيْهِ، وَإِذَا وَقَعَ بِأَرْضٍ وَأَنْتُمْ بِهَا فَلَا تَخْرُجُوا فِرَارًا مِنْهُ
“If you hear of it [the plague] in a land, do not go to it; and if it breaks out in a land you are already in, do not leave fleeing from it.” (meaning, not a literal translation)
Reported during Caliph 'Umar's journey to Syria, when he turned back on hearing of an outbreak there after consulting the companions on this hadith.
Classical and modern commentators alike read this as an early articulation of movement restriction to contain contagion — staying put rather than either advancing into or fleeing an outbreak zone.