Sahih Bukhari Volume 8, Book 75, Hadith Number 413.

Narated By ‘Amr bin Maimun : Whoever recites it (i.e., the invocation in the above Hadith (412) ten times will be as if he manumitted one of Ishmael’s descendants. Abu Aiyub narrated the same Hadith from the Prophet saying, “(Whoever recites it ten times) will be as if he had manumitted one of Ishmael’s descendants.”