It is narrated from Hazrat Abu Ayyub Ansari (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: Whoever recites these words ten times — "La ilaha illallah wahdahu la sharika lahu, lahul mulk wa lahul hamd wa huwa 'ala kulli shay'in qadeer" — it is like freeing one or ten slaves.
Hadith Referenceمسند احمد / مسند الأنصار رضي الله عنهم / 23546