Is it acceptable to clean one’s nose during Salah?

Al-Amal al-Kathĩr (excessive movement) invalidates the Salāh. Imam al-Haskafi (d.1088 AH) writes that there are 5 opinions as to what al-Amal al-Kathĩr means. Imam Ibn Abidĩn (d.1252 AH) comments that the Sahĩh (correct) opinion is that when a person is performing Salāh and he does such an action that somebody from afar looks and is left in no doubt that this person is not in Salāh, then this will be deemed as al-Amal al-Kathĩr and will invalidate the Salāh.Imam al-Kāsāni (d.587 AH) authenticated this opinion and Imam al-Zayla’i (d.743 AH) narrates the same position.

Another definition that has been discussed amongst the Fuqahāsuch as Imam al-Haskafi (d.1088 AH) is that al-Amal al-Kathīr means doing such an action in Salāh that is normally done with 2 hands outside of Salāh,even if a person performed this action with one during Salāh. The different explanations of al-Amal al-Kathīr also been narrated by Ibn Māzah al-Bukhari (d. 616 AH) from the Mashāyikh of the Madhhab.

The Binā’ (basis) for al-Amal al-Kathīrbeing an invalidating action is that in Salāh,mundane worldly acts all become prohibited. Imam al-Kāsānī (d.587 AH) and others discuss that only those actions that are from the practices of Salāhcan be performed in the period of Salāh. It is as though a person is temporarily disconnected from this world and in a higher station and realm during Salāh; the actions of that realm are all taught to us by the Prophet ﷺ and are Ta’abbudīand restricted to what was narrated to us, as described by al-Sighnaqi (d. 711 AH).When a person performs actions which are foreign to Salāhwhich are deemed excessive and gross (al-Amal al-Kathĩr), it will relegate the individual back to this mundane world and life. As such, the sacred union of Salāh with Allah is invalidated.