Praise be to Allah.
Du’aa’ for completing the Qur’aan in the manner asked about here is a reprehensible innovation (bid’ah), which was not done by the Prophet (peace and blessings of Allaah be upon him) or by the righteous salaf (may Allaah be pleased with them). If it had been something good, they would have done it before us.
Rather what is narrated from the salaf is to make du’aa’ after completing the Qur’aan, without stipulating any specific du’aa’ or any particular way of doing it. So if the Muslim completes the Holy Qur’aan, whether in Ramadaan or at other times, it is mustahabb for him to raise his hands and call upon Allaah, asking Him for the best in this world and in the Hereafter.
Shaykh Ibn Baaz (may Allaah have mercy on him) was asked:
Is there a specific du’aa’ for completing the Qur’aan?
There is no evidence that there is a specific du’aa’ for this as far as I know. Hence it is permissible for a person to make du’aa’ as he wishes and to choose beneficial supplications such as praying to be forgiven, to be granted Paradise and to be saved from Hell, seeking refuge with Allaah from fitnah (temptation, tribulation), asking for help to understand the Qur’aan in the manner that Allaah is pleased with and to act upon it and memorize it, etc., because it was proven that Anas (may Allaah be pleased with him) used to gather his family when he completed the Qur’aan and make du’aa’.
Majmoo’ Fataawa Ibn Baaz, 11/358.
With regard to reciting that over food and distributing it, and doing that when someone dies and on Thursdays, all of that is bid’ah (innovation).
The Prophet (peace and blessings of Allaah be upon him) has commanded us to adhere to his Sunnah and the way of the Rightly-Guided caliphs, and he has forbidden us to introduce innovations into the religion. He has told us that this is misguidance, and that bid’ahs will be rejected and thrown back at the one who does them, and he will not be rewarded for them.
Abu Dawood (4607) narrated from al-‘Irbaad ibn Saariyah that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever among you lives after I am gone will see great differences. I urge you to adhere to my Sunnah and the way of the Rightly-Guided caliphs. Adhere to it and cling firmly to it. And beware of newly-innovated matters, for every newly-innovated matter is a bid’ah, and every bid’ah is a going-astray.” Classed as saheeh by al-Albaani in Saheeh Abi Dawood, 3851.
The Prophet (peace and blessings of Allaah be upon him) said: “Whoever does any action that is not in accordance with this matter of ours (Islam) will have it rejected.” Narrated by Muslim, 1718.
And Allaah knows best.