Answered by Shaykh Faraz Rabbani
Question : Does vomiting break the ritual ablution? Further, is it considered filthy and is the same ruling of filth applied to a baby’s vomit?
Answer : 1. Vomit, including baby vomit, is only considered filthy if it is more than a mouthful, with a mouthful being defined as that which the mouth (of the one vomiting) would not be able to hold in without undue difficulty.
Imam `Ala’ al-Din al-Haskafi stated in his Durr al-Mukhtar Sharh Tanwir al-Absar, the most important commentary in Hanafi fiqh for relied upon rulings and all the conditions and details related to them, and amazing in its conciseness:
“(And) wudu is nullified (by vomit that fills the mouth) such that it could only be kept in with difficulty.”
This was confirmed by Ibn Abidin in his Radd al-Muhtar, where he cited several authorities who chose this definition.
2. If the baby vomits more than a mouthful, and it gets on the clothes, note that a small amount of it is excused for the purposes of prayer.
It is recommended, whenever reasonably possible to remove such an amount before one prays, but if one does not remove it the prayer is still valid. It is neither blameworthy nor sinful not to remove a small amount of filth before prayer, though one would have left that which is best. This is a great dispensation for many, especially mothers with small children.
The amount excused is the equivalent of about 4 or 5 grams of solid filth, or the extent of the area of the inner palm (around 5 cm in diameter) for liquid filth. Note that it is not needed to measure this; one’s judgement is enough. Eventually, of course, one needs to remove the filth, so it does not spread…
[ref: Ibn Abidin, Radd al-Muhtar; Shurunbulali, Maraqi al-Falah]
And Allah knows best.