Is there any proof for reciting ‘Sadaqallahul Azim’ after reciting the Quran?
I have not come across any such clear proof. Despite this, there will be no harm in reciting it as long as one does not regard it to be binding or Sunnah.
This is actually a response and expression of one’s belief in the Quran being the true word of Allah. There is undoubtedly no harm in such expressions.
Rasulullah (sallallahu’alayhi wasallam) while reciting Quran in [nafl] salah even, would utter words in response to the words being recited:
Sayyiduna Hudhayfah (radiyallahu’anhu) reports that he offered tahajjud salah behind Nabi (sallallahu’alayhi wasallam) one night. He says: ‘…Whenever Nabi (sallallahu’alayhi wasallam) passed a verse that mentioned a tasbih, he (sallallahu’alayhi wasallam) would recite a tasbih. When he (sallallahu’alayhi wasallam) passed a spot that required one to beg from Allah, he begged, and when he passed a verse that required one to seek protection [of Allah] he would do so.’
(Sahih Muslim, Hadith: 1811)
In this narration we are thought to respond to the verses that we recite, based on their specific meaning during the recital.
Thus, for one to respond to the recital in general after the recital should not be considered any different.
And Allah Ta’ala Knows best,
Answered by: Moulana Muhammad Abasoomar