Mustadrak al-Hakim — Hadith 1996

It is narrated from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever goes out to the market and says: 'Ashhadu an la ilaha illallahu wahdahu la sharika lah, lahul-mulku wa lahul-hamd, yuhyi wa yumit, wa huwa hayyun la yamut, bi yadihil-khayr, wa huwa 'ala kulli shay'in qadir' (I bear witness that there is no god but Allah, alone, without partner; His is the dominion and His is all praise; He gives life and causes death; He is Ever-Living and will never die; all good is in His hand, and He has complete power over all things), Allah Almighty records for him a million good deeds, erases from him a million sins, and builds for him a house in Paradise."
Abdullah bin Wahb narrated it in this way, whereas Isma'il bin Ayyash narrated it from Salim through Umar bin Muhammad bin Zayd.