Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) said: "O Banu Talhah, take it forever, generation after generation; none will take it from you except a wrongdoer." - that is, the custodianship (service) of the keys of the Ka'bah.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11188