In one narration the wording is: Whoever recites these words: 'La ilaha illallahu wahdahu la sharika lahu, lahul-mulku wa lahul-hamdu, wa huwa 'ala kulli shay'in qadir' (There is no deity except Allah; He alone is the deity, He has no partner; to Him alone belongs the dominion, to Him alone belongs all praise, and He has power over all things), whoever recites these words ten times, it will be for him like freeing a slave. Here the narrator is in doubt about a word.
(Allamah Haythami says:) I say:
Tirmidhi recorded this narration in abridged form, mentioning the recitation of 'La ilaha illallah' and its reward. Ahmad recorded both these narrations, and the narrators of both are the narrators of the Sahih.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأذكار / 16823