"O Messenger of Allah, what do you think I should say in my supplication, if I come upon Laylatul-Qadr?" He said: "Say: 'Allahumma innaka 'afuwwun tuhibbul-'afwa, fa'fu 'anni (O Allah, You are Forgiving and love forgiveness, so forgive me).'" (Using translation from Ibn Mājah 3850)   

قُلْتُ لِلنَّبِيِّ ﷺ أَرَأَيْتَ إِنْ عَلِمْتُ لَيْلَةَ الْقَدْرِ مَا أَقُولُ؟ قَالَ قَوْلِي اللهُمَّ إِنَّكَ عَفُوٌّ تُحِبُّ الْعَفْوَ فَاعْفُ عَنِّي