Sayyiduna Uthman (may Allah be pleased with him) narrated: The Prophet (peace and blessings be upon him) said: "Whoever does any good to anyone from the descendants of Abd al-Muttalib, and that person is unable to repay him for it in this world, then tomorrow, when he meets me, it will be my responsibility to repay him."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Abd al-Rahman bin Abi al-Zinad, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب المناقب / 15017