Sahih Muslim 2220 a
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
There is no infection, no safar, no hama. A desert Arab said: Allah's Messenger, how is it that when the camel is in the sand it is like a deer-then a camel afflicted with scab mixes with it and it is affected by sub? He (the Holy Prophet) said: Who infected the first one? Note: The majority of scholars interpret this to mean that these things in and of themselves do not transmit or cause harm through supernatural or hidden means but that Allah is ultimately in control and any fearful superstition around these is false.
حَدَّثَنِي أَبُو الطَّاهِرِ، وَحَرْمَلَةُ بْنُ يَحْيَى، - وَاللَّفْظُ لأَبِي الطَّاهِرِ - قَالاَ أَخْبَرَنَا 
 ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، قَالَ ابْنُ شِهَابٍ فَحَدَّثَنِي أَبُو سَلَمَةَ بْنُ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي،
 هُرَيْرَةَ حِينَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ لاَ عَدْوَى وَلاَ صَفَرَ وَلاَ هَامَةَ ‏"‏ ‏.‏ فَقَالَ
 أَعْرَابِيٌّ يَا رَسُولَ اللَّهِ فَمَا بَالُ الإِبِلِ تَكُونُ فِي الرَّمْلِ كَأَنَّهَا الظِّبَاءُ فَيَجِيءُ الْبَعِيرُ الأَجْرَبُ
 فَيَدْخُلُ فِيهَا فَيُجْرِبُهَا كُلَّهَا قَالَ ‏"‏ فَمَنْ أَعْدَى الأَوَّلَ ‏"‏ ‏.‏