The Ruling on saying "Allah, the Magnificent, Has Spoken The Truth" After Recitation
Question :
What is the ruling on saying "Allah, the Magnificent, has Spoken the truth" after reciting the Qur'an?
Answer:
To say Sadaq Allahu Al-'Azim "Allâh the Magnificent has Spoken the truth" after reciting the Noble Qur'an has no basis for it in the Sunnah nor in the actions of the Companions, may Allah be pleased with them. It was merely initiated in later times. There is no doubt that the one saying, "Allâh the Magnificent has Spoken the truth" is praising Allâh Almighty. So this is a form of worship, and in the case of worship; it is not allowed for us to worship Allâh except with what there is a Shari 'ah evidence for. Since there is no proof from the Shari'ah in this case, then saying it after recitation is not legislated, nor prescribed, so it is not prescribed for a person to say it after reciting the Noble Qur'an.
Someone might say: Didn't Allah Almighty say :
"Say: Allah has spoken the truth."
We would answer that yes, Allah Almighty did say this, and yes, we say, "Allâh has spoken the truth," but did the Messenger of Allah ﷺ say, "When you finish reciting the Qur'an, say: Allah Almighty has spoken the truth."?
What is authentic is that once Ibn Mas'ud, may Allah be pleased with him, recited Surat An-Nisa' to the Prophet ﷺ When he reached, "How (will it be) then, when We bring from each nation a witness and We, bring you (O Muhammad) as a witness against the people."
Then the Prophet ﷺ said : "(That is) enough for you."
He didn't say, "Say: Allah has spoken the truth," nor did Ibn Mas'ud say it. This is an evidence that it is not legislated for one to say "Allah the Magnificent has Spoken the truth" after reciting the Qur'an.
Suppose that something happens to confirm what Allah Almighty and His Messenger ﷺ said in such an instance, you may say, "Allâh, the Almighty, has spoken the truth," because you have said this to announce that Allah's Speech is truthful. So for example, if you see someone who is so busy with his children, that he neglects his worship, you may say, "Allah, the Almighty, has spoken the truth" - for He Almighty says:
"Your wealth and your children are only a trial, whereas Allah Almighty! With Him is a great reward (Paradise)."
In similar such cases then there would be no harm.
Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 7 Pages 30-31-32