Here is a benefit on what to say when you finish reciting the Quran. Unfortunately, the innovation of reading (صدق الله العظيم) has become very widespread. The Sunnah is the following:

Aisha radiallahu anha said:

ما جلس رسول الله – صلى الله عليه وعلى آله وسلم – مجلسا ، ولا تلى قرآن ، ولا صلى صلاة ، إلا ختم ذلك بكلمات ، قالت : فقلت : يا رسول الله أراك ما تجلس مجلسا ولا تتلو قرآنا ، ولا تصلى صلاة ، إلا ختمت بهؤلاء الكلمات قال : نعم ، من قال خيرا ختم له طابع على ذلك الخير ، ومن قال شرا ، كن له كفارة : سبحانك وبحمدك ، لا إله إلا أنت ، أستغفرك وأتوب إليك

The Messenger of Allah sallahu alayhi wa salam did not sit in a sitting, or recite Quran, or pray a prayer except he completed it with those words. So I said: Oh Messenger of Allah, I see that you do not sit in a gathering or recite Quran or pray a prayer except you complete with the following words. He said: Yes. Whoever says good, it will complete it for him and will be a seal for that good. And whoever said evil, it will be an expiation for him:

سبحانك وبحمدك ، لا إله إلا أنت ، أستغفرك وأتوب إليك

O Allah, You are free from every imperfection; praise be to You. I testify that there is no true god except You; I ask Your Pardon and turn to You in repentance

[Reported by Nasai in Amal ul-Yawm wa Laylah and graded Saheeh by Shaikh Wad’iee in Saheeh Musnad no. 1598]

Imam Nasaai rahimahullah placed (this hadith in) the chapter:

ما ختم تلاوة القرآن

“What to complete the recitation of the Quran with [i.e. what to say]”

[Sunan al-Kubra (6/84)]
So this is what should be read when one is finished reciting the Quran and not
(صدق الله العظيم)

Hassan ibn ‘Attiyah rahimahullah spoke the truth when he said:

ما ابتدع قوم بدعة في دينهم إلا نزع الله من سنتهم مثلها

“A people do not innovate in their religion an innovation, except Allah will remove from their Sunnah something similar”

[Reported by ad-Daarami no. 99 and the chain is Saheeh]

So let us replace the innovation by returning to the Sunnah.

Allah says:

لَّقَدْ كَانَ لَكُمْ فِى رَسُولِ اللَّهِ أُسْوَةٌ حَسَنَةٌ لِّمَن كَانَ يَرْجُو اللَّهَ وَالْيَوْمَ الاٌّخِرَ وَذَكَرَ اللَّهَ كَثِيراً

Indeed in the Messenger of Allah (Muhammad) you have a good example to follow for him who hopes in (the Meeting with) Allah and the Last Day and remembers Allah much

[33:21]

Translated by

Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan