اللَّهُمَّ لاَ تُؤَاخِذْنِي بِمَا يَقُولُونَ وَاغْفِرْ لِي مَا لاَ يَعْلَمُونَ [وَاجْعَلْنِي خَيْرًا مِمَّا يَظُّنُّونَ]
Allāhumma lā tu'ākhidhnī bimā yaqūlūn, waghfir lī mā lā ya`lamūn [waj`alnī khayran mimmā yaẓunnūn].
O Allah, do not call me to account for what they say and forgive me for what they have no knowledge of [and make me better than they imagine].
Al-Bukhari, Al-'Adabul-Mufrad no. 761. See Al-Albani, Sahih Al-'Adabul-Mufrad (no. 585). The portion between brackets if from Al-Bayhaqi, Shu'ab Al-Iman 4/228, and comes another account.