Divination and Omens (Kitab Al-Kahanah Wa Al-Tatayyur)
Dawud :: Book 29 : Hadith 3955
Narrated Marrah ibn Ka'b:
Amr ibn Abasah, said that Marrah ibn Ka'b said: I heard the Apostle of Allah (peace_be_upon_him) say: If anyone emancipates a Muslim slave, that will be his ransom from Jahannam.