akhi it is not a sunnah lol where did you get that from, It is Bidah its not mentioned no where. Please read the Following Fatawah:
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Saying "sadaq Allaahul-'Adtheem" after finishing reading the Qur'ân
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Question: What is the ruling regarding the saying of "sadaq Allaahul-'Adtheem" after finishing reading of the Qur'ân?
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Response: All Praise is for Allaah, the One, and prayers and salutations upon His Messenger, his family and his companions. To proceed:
The saying of "sadaq Allaahul-'Adtheem" after finishing reading of the Qur'an is an innovation. The Prophet (sal-Allaahu `alayhe wa sallam) did not do this and nor did the Rightly Guided Khulafaa, nor any of the (other) Companions (radhi-yallaahu 'anhum) and nor the Imaams of the (Pious) Predecessors (rahima-humullaah). This being with their vast reading and assistance in spreading it's (the Qur'ân's) message and knowing it's rulings. So the saying of this and adhering to it after finishing the reading (of the Qur'ân) is an innovation. It has been confirmed on the authority of the Prophet (sal-Allaahu `alayhe wa sallam) that he said:
((Anyone who introduces something into this matter of ours (i.e. Islaam), that which is not from it, will have it rejected)) - this (narration) is agreed upon (by both Imaam al-Bukhaaree and Imaam Muslim).
And in another narration:
((Anyone who does an act which is not in agreement with us, then he will have it rejected)) - narrated by Muslim.
And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet (sal-Allaahu `alayhe wa sallam) and his family and his companions.
The Permanent Committee for Islaamic Research and Fataawa
The current members of the Permanent Committee include:
Head: Shaykh 'Abdul 'Azeez Aal ash-Shaykh;
Deputy Head: Shaykh 'Abdullaah Ibn Ghudayyaan;
Member: Shaykh 'Abdullaah Ibn Qu'ood;
Member: Shaykh 'Abdullaah Ibn Munay;
Member: Shaykh Saalih Ibn Fowzaan;
Member: Shaykh Bakar 'Abdullaah Abu Zayd.
Amongst the members who have passed away include:
Shaykh Ibraaheem Ibn Muhammad Aal ash-Shaykh;
Shaykh 'Abdul 'Azeez Ibn Baaz;
Shaykh 'Abdur-Razzaaq Ibn 'Afeefee.
al-Bid'u wal-Muhdathaat wa maa laa Asla lahu - Page 571;
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-'Ilmiyyah wal-Iftaa. - Fatwa No. 3303
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This is the answer Sheikh Bin Baz gave to a question on the status of saying "sadaqa allahu al-atheem" after reciting Qur'an according to the way of the Salaf-us-Salih:
"Praise be to Allah.
I do not know any basis for the people's habit of saying "sadaqa allahu al-atheem" when they finish reading Qur'an, so it should not be taken as a habit. Indeed according to the principles of sharee'ah it is more like bida'a, if any believes it is sunnah. So this should not be done and shouldnot be taken as a habit.
With regard to the ayat: "Say O Muhammad: Allah has spoken the truth"
(Al-Imran 3:95) - this is not speaking about this matter. Rather Allah was commanding him to explain to the people that Allah has spoken the truth in what he has said, in His books, the Tawrat, etc., and that he has spoken the truth in all that He had said to His slaves in the Tawrat the Injeel and all other revealed books.
And he was speaking the truth in all that he said his slaves in his book the Qur'an.
But this is not evidence that it is mustahabb to say "sadaqa allahu al-atheem" after reading the Qur'an or after reading some ayahs or a surah.
This is not reported or known from the Prophet SAWS or his companions (radi allahu anhum).
When Ibn Masood recited to the Prophet SAWS from the beginning of surat ul nisa'a until he reached the ayat:
"How will it be then, when we bring from each nation a witness and we bring you o muhammad as a witness against these people?"
the Prophet SAWS said to him "Enough"
Ibn Masood said: "I turned and saw that his eyes were filled with tears", i.e. he was weeping of the mention of this great status on the Day of Resurrection which is mentioned in this ayat, Where Allah says: "How will it be then, when we bring from each nation a witness and we bring you - O Muhammad - as a witness against these people" (i.e. his ummah)
The point here is that there is no basis in sharee'ah for adding these words "sadaqa allahu al-atheem" when finished reading the Qur'an. What is prescribed is not to do this, in accordance with the example of the Prophet SAWS and his companions (radi allahu anhum). But if a person does that sometimes, without intending to, it doesn't matter, for Allah speaks the truth in all matters, may he be glorified and exalted. But making a habit every time one reads the Qur'an, as many people do now adays, has no basis, as stated above."
Kitaab Majmoo Fatawaa wa Maqaalat Mutanaawi'ah li Samaahat Ash-Sheikh Al-Ulamaa Abdul Aziz Ibn Abdullah Ibn Baz
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http://www.allaahuakbar.net/quran/sadaqallaahuladtheem.htm
www.islam-qa.com
As-Salaam 3laikum Wa Ra7matullahi Wa Barakatu
