Musannaf Ibn Abi Shayba 3:4898

Waki’ narrated to us, from ‘Abd al-Jabbar ibn ‘Ayyash, from Qays ibn Wahb, from Murrah, from ‘Abdullah, who said: "Whoever prays four [rak'ahs] after the 'Isha' [prayer], not separating between them with a taslim, they are equivalent to their like from the Night of Decree (Laylat al-Qadr)."