Hadith: Shall I not teach you some words which the Messenger of Allah (may Allah’s peace and blessings be upon him) taught me, (it will surely prove so useful) that if you have a debt as large as a mountain, Allah will surely pay it on your behalf? Say: O Allah, Grant me enough of what You make lawful so that I may cast aside what You make unlawful, and bestow upon me Your favor so that I may dispense with all but You

عن علي - رضي الله عنه-: أن مُكَاتَبًا جاءه فقال: إني عَجَزْتُ عن كتابتي فَأَعِنِّي، قال: ألا أعلمك كلمات عَلَّمَنِيهِنَّ رسولُ الله صلى الله عليه وسلم لو كان عليك مثلَ جبلٍ دَيْنًا أَدَّاهُ الله عنك؟ قل: «اللهم اكْفِنِي بحلالك عن حرامك، وأَغْنِنِي بفضلك عَمَّنْ سِوَاكَ».
[حسن] - [رواه الترمذي وأحمد]

‘Ali (may Allah be pleased with him) reported that a slave who had made a contract with his master to pay for his freedom, came to him and said: "I am unable to fulfill my obligation (of paying for my freedom to my master), so help me." ‘Ali (may Allah be pleased with him) said to him: "Shall I not teach you some words which the Messenger of Allah (may Allah’s peace and blessings be upon him) taught me, (it will surely prove so useful) that if you have a debt as large as a mountain, Allah will surely pay it on your behalf? Say: O Allah, Grant me enough of what You make lawful so that I may cast aside what You make unlawful, and bestow upon me Your favor so that I may dispense with all but You)."
Hasan/Sound. - [At-Tirmidhi]

Explanation

This Hadīth narrates a story about a slave who made a contract with his master to pay him for his emancipation in installments, but he had no money to pay his master. He went to ‘Ali ibn Abi Tālib (may Allah be pleased with him) so that he might help him pay off his debt. ‘Ali (may Allah be pleased with him) guided him to this divine remedy, which is a supplication that the Prophet (may Allah's peace and blessings be upon him) taught him to say. Whoever says it sincerely, Allah will pay off his debt on his behalf, even if it is as huge as a mountain. He told him to say: "O Allah, Grant me enough of what You make lawful so that I may cast aside what You make unlawful, and bestow upon me Your favor so that I may dispense with all but You.”