It is narrated from Sayyiduna Abu Ayyub (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever says ten times after the Fajr prayer: 'La ilaha illallahu wahdahu la sharika lah, lahul-mulku wa lahul-hamdu wa huwa 'ala kulli shay'in qadir' (There is no god but Allah, alone, without partner; His is the dominion and His is the praise, and He has power over all things), it will be for him equal to freeing four slaves from the descendants of Isma'il (peace be upon him)."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 4000