Supplications before ending the prayer
اَللّٰهُـمَّ إِنِّيْٓ أَسْأَلُـكَ يَآ اَللهُ بِأَنَّـكَ الْوَاحِـدُ الْأَحَـدُ، الصَّـمَدُ الَّـذِيْ لَـمْ يَلِـدْ وَلَمْ يُوْلَدْ، وَلَمْ يَكـنْ لَّهٗ كُـفُوًا أَحَـدٌ، أَنْ تَغْـفِرْ لِيْ ذُنُـوْبِيْ إِنَّـكَ أَنْـتَ الْغَفُـوْرُ الرَّحِـيْمُ
O Allah, I ask You. O Allāh, You are the One, the Only, Self-Sufficient Master, Who was not begotten and begets not and none is equal to Him. Forgive me my sins; surely you are The Forgiving, Merciful.
References
[Sunan Nasai - 1302]