Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "The feet of a servant will not move on the Day of Resurrection until he is asked about four things: about his life, in what he spent it; about his youth, how he used it up; about his wealth, from where he earned it and on what he spent it; and about his knowledge, what he did with it."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17247