It was narrated from 'Aishah that she said: "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)”"
SahihSahihHasan SahihBook 34 · Hadith 24