The Prophet ﷺ said, 'No 'Adwa (i.e. no contagious disease is conveyed to others without Allah's permission); nor (any evil omen in the month of) Safar; nor Hama" A bedouin said, "O Messenger of Allah ﷺ! What about the camels which, when on the sand (desert) look like deers, but when a mangy camel mixes with them they all get infected with mange?" On that Allah s Apostle said, "Then who conveyed the (mange) disease to the first (mangy) camel?" (Using translation from Bukhārī 5770)
عَنِ النَّبِيِّ ﷺ قَالَ «لَا عَدْوَى وَلَا هَامَةَ وَلَا صَفَرَ» فَقَالَ الْأَعْرَابِيُّ فَمَا بَالُ الْإِبِلِ تَكُونُ فِي الرَّمَلِ كَأَنَّهَا الظِّبَاءُ فَيُخَالِطُهَا الْبَعِيرُ الْأَجْرَبُ فَيُجْرِبُهَا؟ قَالَ النَّبِيُّ ﷺ «فَمَنْ أَعْدَى الْأَوَّلَ؟»