Some scholars are of the view that vomiting does not invalidate wudoo’, such as Imam Abu Haneefah and Imam Ahmad. But Ahmad stipulated that vomiting does invalidate wudoo’ if there is a large amount of vomit.
Imam al-Shaafa’i was of the view that vomiting does not invalidate wudoo, and this is the correct view, because there is no sound evidence to show that vomiting invalidates wudoo’.
See: al-Majmoo’, 2/63-65; al-Mughni, 1/247-250
Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) was asked: Does whatever comes out of anything other than the front and back passages invalidate wudoo’?
What comes out of anything other than the front and back passages does not invalidate wudoo’, whether it is a little or a lot, except urine and stools. That is because the basic principle is that it does not invalidate wudoo’. Whoever claims something that is contrary to the basic principle has to provide evidence, but it is proven that man is taahir by the shar’i evidence, and whatever is proven by the shar’i evidence cannot be altered except by further shar’i evidence. We do not go beyond what is indicated by the Book of Allaah and the Sunnah of His Messenger (peace and blessings of Allaah be upon him), because we submit to the laws of Allaah, not to our whims and desires. So there is no justification for making people purify themselves when it is not essential and we do not waive from them a purification that is obligatory.
If someone were to say that it is narrated that the Prophet (peace and blessings of Allaah be upon him) vomited then did wudoo’, we say: this hadeeth has been classed as da’eef by most of the scholars. Then we say that this is simply an action, and the fact that the Prophet (peace and blessings of Allaah be upon him) simply did an action does not indicate that it is obligatory, because there is no clear instruction. Moreover it is contradicted by another hadeeth – even if it is da’eef – which says that the Prophet (peace and blessings of Allaah be upon him) was treated with cupping then he prayed and did not do wudoo’. This indicates that it is not obligatory to do wudoo’ after vomiting.
This is the correct view, that whatever comes out from the body does not invalidate wudoo’ even if it is a lot, whether it is vomit, saliva, blood, pus or anything else, unless it is urine or stools, such as if an opening is made in the body to let them out, in which case wudoo’ is invalidated when they come out from that opening. End quote.
Majmoo’ Fataawa Ibn ‘Uthaymeen, 11/198.