Musnad Ahmad 1153:1723

Waki' narrated to us, Kahmas narrated to us, from Abdullah ibn Buraydah, from Aisha, that she said: "O Messenger of Allah, what do you think if I encounter the Night of Decree (Laylat al-Qadr), what should I supplicate with?" He said: "You say: 'O Allah, indeed You are Pardoning, You love pardon, so pardon me.'"