Musannaf Ibn Abi Shayba 3:5441

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Ubaydullah ibn Abd al-Rahman ibn Wahb narrated to us, from Muhammad ibn Ka’b al-Qurazi, he said: Whoever recites in the voluntary prayer of Duha "Say, He is Allah, [who is] One" ten times, a house will be built for him in Paradise.