Musannaf Ibn Abi Shayba 3:4897

Muhammad ibn Fudayl narrated to us, from al-Ala’ ibn al-Musayyab, from Abd al-Rahman ibn al-Aswad, from his father, from Aisha, who said: "Four [rak'ahs] after the Isha [prayer] are equivalent to their like from the Night of Decree (Laylat al-Qadr)."