Reward equal to that of freeing four precious slaves

"He who utters ten times: 

'La ilaha illallahu, wahdahu la sharika lahu, lahulmulku wa lahulhamdu, wa Huwa 'ala kulli sha'in Qadir'

There is none worth of worship except Allah. He is One and He has no partner with Him. His is the sovereignity and His is the praise, and He is Omnipotent.

he will have a reward equal to that for freeing four slaves from the progeny of Prophet Ismail."

[narrated Bukhari and Muslim]