اللّهُـمَّ إِنِّـي أَسْأَلُـكَ يا اللهُ بِأَنَّـكَ الواحِـدُ الأَحَـد الصَّـمَدُ الَّـذي لَـمْ يَلِـدْ وَلَمْ يولَدْ، وَلَمْ يَكـنْ لَهُ كُـفُواً أَحَـد ، أَنْ تَغْـفِرْ لي ذُنـوبي إِنَّـكَ أَنْـتَ الغَفـورُ الرَّحِّـيم
Allāhumma innī as'aluka yā Allāh bi'annaka ‘l-Wāḥidu ‘l-Aḥaduṣ-ṣamad, alladhī lam yalid wa lam yūlad, wa lam yakun lahu kufuwan aḥad, an taghfir lī dhunūbī, innaka anta ‘l-Ghafūrur-Raḥīm.
O Allah, I ask You. O Allah, 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 Forgiving, Merciful.
An-Nasa'i 3/52, Ahmad 4/338. See also Al-Albani, Sahih An-Nasa'i 1/280 and Sifat Salatun-Nabi, pg. 204.