It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that a mukatab slave (one who has contracted to pay for his freedom) came to him and said, "Help me with my payment." He said: "Shall I not teach you words which the Messenger of Allah (peace and blessings be upon him) taught me? Even if you owed a debt as large as Mount Sir, Allah would pay it off on your behalf. Say: 'Allahummakfini bi halalika 'an haramik, wa aghnini bi fadlika 'amman siwak' (O Allah, suffice me with what You have made lawful, keeping me away from what You have made unlawful, and by Your grace make me independent of all besides You)." The chain of this hadith is sahih (authentic), but the two Shaykhs did not record it.