Musnad Ahmad 26:648

'Abd al-Rahman narrated to us, Sufyan narrated to us, from 'Amarah ibn al-Qa'qa', he said: Abu Zur'ah narrated to us, a companion of ours narrated to us, from 'Abdullah ibn Mas'ud, he said: The Messenger of Allah (may Allah bless him and grant him peace) stood among us and said: "Nothing transmits [disease] to anything, nothing transmits to anything, nothing transmits to anything." A Bedouin stood up and said: "O Messenger of Allah, a spot of mange occurs on the lip of a camel or its tail among a large herd of camels, and then they all become mangy?" The Messenger of Allah (may Allah bless him and grant him peace) said: "Then what made the first one mangy? There is no contagion, no [superstition regarding] the owl, and no [superstition regarding] Safar. Allah created every soul, and He wrote its life, its calamities, and its provision."