Here’s something to say when you’ve finished reciting the Quran. Unfortunately, the invention of reading (صدق الله العظيم) has grown immensely popular. The following is the Sunnah:
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 Prophet Muhammad, sallahu alayhi wa salam, never sat in a sitting, recited the Quran, or said a prayer until he finished it with such words. So I replied to him, “Oh Messenger of Allah, I observe that you do not sit in a gathering, recite the Quran, or offer a prayer until you finish with these words.” Yes, he replied. Whoever talks good will accomplish the task for him and serve as a seal for that good. And anyone uttered something bad will be punished:
سبحانك وبحمدك ، لا إله إلا أنت ، أستغفرك وأتوب إليك
Allah, You are faultless and without flaws; praise be to You. I declare that You are the one genuine god; I beg Your forgiveness and turn to You in repentance.
[Nasai reported it in Amal ul-Yawm wa Laylah, and Shaikh Wad’iee rated it Saheeh in Saheeh Musnad no. 1598]
اللَّهُمَّ إِنِّي أَشْهَدُ أَنَّ هَذَا كِتَابُكَ الْمُنْزَلُ مِنْ عِنْدِكَ عَلَى رَسُولِكَ مُحَمَّدِ بْنِ عَبْدِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَ آلِهِ
O Allah, I swear that this is the Book that Thou hast given to Thy Messenger Muhammad bin Abdillah, may Allah’s blessings be upon him and his offspring;
وَ كَلاَمُكَ النَّاطِقُ عَلَى لِسَانِ نَبِيِّكَ جَعَلْتَهُ هَادِياً مِنْكَ إِلَى خَلْقِكَ وَ حَبْلاً مُتَّصِلاً فِيمَا بَيْنَكَ وَ بَيْنَ عِبَادِكَ
(These are) Thy Words, which Thou gave speech to via Thy Prophet, whom Thou designated as a Guide for the people and an unbroken bond of protecting friendship between Thee and Thy followers.
اللَّهُمَّ إِنِّي نَشَرْتُ عَهْدَكَ وَ كِتَابَكَ اللَّهُمَّ فَاجْعَلْ نَظَرِي فِيهِ عِبَادَةً وَ قِرَاءَتِي فِيهِ فِكْراً وَ فِكْرِي فِيهِ اعْتِبَاراً
I make public Thy testament and Thy Book, O Allah. O Allah, please allow me to devote my complete attention to (this) lovely religious task; please allow me to observe and learn from (this) careful meditation.
وَ اجْعَلْنِي مِمَّنِ اتَّعَظَ بِبَيَانِ مَوَاعِظِكَ فِيهِ وَ اجْتَنَبَ مَعَاصِيَكَ
Let me be one of those who heed Thy straightforward warnings and teachings provided in this Book, and abstains from what Thou has made illegal.
وَ لاَ تَجْعَلْ نَظَرِي فِيهِ غَفْلَةً وَ لاَ قِرَاءَتِي هَذَراً إِنَّكَ أَنْتَ الرَّءُوفُ الرَّحِيمُ
Allow neither my focus nor my recital to lapse into a crazy babble. Merciful, you are indeed full of sympathy.