Musnad Ahmad 1153:1366

Muhammad ibn Ja'far narrated to us, Kahmas narrated to us, he said: Ibn Buraydah narrated to me, he said: 'Aishah said: "O Prophet of Allah, what do you think if I encounter the Night of Decree (Laylat al-Qadr), what should I say?" He said: "You say: 'O Allah, indeed You are Pardoning, You love pardon, so pardon me.'"