What is the sound evidence for the impurity of vomit? And may Allah reward you with goodness.

Vomit is considered impure by the majority of jurists because it is food that has transformed in the stomach into something putrid or spoiled, thus resembling feces in ruling. There is also a very weak hadith narrated by Ammar, elevated to the Prophet (peace be upon him): "O Ammar, a garment is only washed from five things: feces, urine, vomit, blood, and semen."