Musannaf Ibn Abi Shayba 3:6372

Yahya ibn Sa'id narrated to us, from Sufyan, from Abu Ishaq, from 'Asim ibn Damra, from al-Hasan ibn 'Ali, who said: The "adbar al-sujud" (the aftermath of the prostration) is two rak'ahs after the Maghrib [prayer].