Praise be to Allah.
Many people have the habit of ending a recitation from the Qur’aan with the words "Sadaqa Allaahu al-‘Azeem (Almighty Allah. has spoken the truth)," but this has no basis in Islam because the Prophet (peace and blessings of Allah. be upon him) did not do it, nor was it the custom of the Sahaabah (may Allah. be pleased with them), and it was unknown among the Taabi’een (the generation after the Sahaabah). This custom arose in later times because some recitors would say these words, on the basis of the ayah: "Say: Allah. has spoken the truth" [Aal ‘Imraan 3:95 – interpretation of the meaning], and people liked this. But this istihsaan (being liked) should be rejected, because if this was really something good, the Prophet (peace and blessings of Allah. be upon him), the Sahaabah and the Taabi’een – the salaf or first and best generations of the ummah – would not have neglected to do it.
The ayah"Say: Allah. has spoken the truth” (Aal ‘Imraan 3:95 – interpretation of the meaning) does not mean that these words should be said at the end of any reading or recitation. If that were the case, He would have said, "When you finish reading, say ‘Allah. has spoken the truth,’" just as He said (interpretation of the meaning): "So when you want to recite the Qur’aan, seek refuge with Allah. from Shaytaan (Satan), the outcast (the cursed one)." [al-Nahl 16:98] The ayah which the innovators use to support their practice of saying "Sadaqa Allah." after reciting Qur’aan was actually revealed in the context of confirming what was said about how all food had been lawful to Bani Isra’eel except what Isra’eel had made unlawful for himself. Allah. said (interpretation of the meaning): "… Say (O Muhammad): ‘Bring here the Tawraat (Torah) and recite it, if you are truthful.’ Then, after that, whosoever shall invent a lie against Allah., such shall indeed be the zaalimoon (disbelievers). Say (O Muhammad), ‘Allah. has spoken the truth; follow the religion of Ibraaheem (Islamic monotheism, i.e., he used to worship Allah. alone), and he was not of al-mushrikeen (polytheists)."[Aal ‘Imraan 3:93-95]
If this ayah meant that these words should be said after reciting from the Qur’aan, the first one to know and do this would have been the Messenger of Allah. (peace and blessings of Allah. be upon him). Because this is not the case, we know that this is not what was meant.
In conclusion, therefore, saying “Sadaqa Allaahu al-‘Azeem” after reciting Qur’aan is an innovation, and the Muslim should not say it.
But believing that Allah. has spoken the truth is obligatory, and whoever disbelieves or doubts the truth of what Allah. has said is a kaafir who is outside of the pale of Islam. We seek refuge with Allah. from that.
f a person says "Allah. has spoken the truth" on certain occasions, such as when something He has foretold comes to pass, affirming the truth of what He has said, then this is permissible, because something similar has been reported in the Sunnah. The Prophet (peace and blessings of Allah. be upon him) was giving a speech, and al-Hasan and al-Husayn came along, so he came down from the minbar, picked them up and put them in from of him, then he said: "Indeed Allah. has spoken the truth: ‘Your wealth and your children are only a trial…’" [al-Taghaabun 64:15 – interpretation of the meaning].
Izaalat al-sitaar ‘an al-jawaab al-mukhtaar by Ibn ‘Uthaymeen, 79-80). ( Answer taken from Islam Question and Answer Library)
2. The Noble Qur'an - Luqman 31:6
And of mankind is he who purchases idle talks (i.e. music, singing, etc.) to mislead (men) from the Path of Allah without knowledge, and takes it (the Path of Allah, the Verses of the Qur'an) by way of mockery. For such there will be a humiliating torment (in the Hell-Fire).