Mukhtasar Bukhari

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) used to say: "The illness of one does not infect another, taking bad omens, considering the owl as a bad omen, and considering the month of Safar as unlucky—all these are baseless thoughts. However, one should keep away from a leper as much as one keeps away from a lion." (Benefit: This is not because the disease of the leper is contagious, but rather, the instruction to keep distance is given so that it may be that Allah had decreed his illness by coincidence, and he became ill. Now, if someone thinks in his heart that he got the disease because he sat with so-and-so, then this is a sin. To save from falling into this sin, as a preventive measure, keeping distance has been advised.)