´It was narrated that 'Ali said:` "I had certain times when I used to come to the Messenger of Allah (ﷺ). When I came to him I would ask for permission to enter. If I found him praying he would clear his throat and I would enter, and if I found him free he would give me permission (to enter)."
Related hadith on this topic
Explanation & Benefits
Hafiz Muhammad Ameen
1214. Commentary: The editor of the book has declared the first two narrations as authentic (sahih) and the third as sound (hasan), but according to other scholars, this ruling is questionable because these narrations are, firstly, disconnected (munqati‘), and secondly, both in chain and text, they are inconsistent (mudtarib). Therefore, all three narrations are weak (da‘if). The basis of these narrations is ‘Abdullah ibn Najji, who is a narrator about whom there is criticism. Yahya ibn Ma‘in states: ‘Abdullah ibn Najji did not hear this narration from ‘Ali radi Allahu anhu. For details, see: [ذخیرة العقبیٰ شرح سنن النسائي : 14/225]
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 1214
Shaykh Safi ur-Rahman Mubarakpuri
Lexical Explanation:
«مَدْخَلَانِ» "Meem" and "Kha" both have a fatha, and the "Dal" in between is sakin (silent). There are two times for presenting oneself in his service.
«تَنَحْنُحِ» To circulate the sound in the throat; to clear the throat.
Benefit:
From this hadith, it is understood that during prayer (salah), making such a sound out of necessity in which there is no articulation of letters does not invalidate the prayer.
Source: Bulugh al-Maram: Commentary by Safiur Rahman Mubarakpuri, Page: 176