Sayyiduna Abdullah (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) said: "Keep remembering the Qur'an, for it slips away from the breast of a man faster than a camel escapes from its rope. And it is very bad for a person to say, 'I have forgotten such and such verse,' rather, it has been made to be forgotten by him."
(Imam Ibn Hibban, may Allah have mercy on him, says:) In this hadith, there is evidence that ability accompanies action, not before it.