It was narrated from Ibn ‘Abbas (رضي الله عنه) that the Messenger of Allah (ﷺ) said:

“No ‘adwa [transmission of infectious disease without the permission of Allah], no tiyarah [superstitious belief in bird omens], no Safar and no ham [refers to a Jahili Arab tradition described variously as: a worm that infests the grave of a murder victim until he is avenged; an owl; or the bones of a dead person turned into a bird that could fly]." Simak said that (the word) Safar referred to a worm in a person's stomach. A man said: O Messenger of Allah, there may be one mangy camel in a hundred, and it transfers the disease to them. The Prophet (ﷺ) said: “Then who infected the first one?"