Sahih Muslim Book 40, Hadith Number 6787.
Chapter : There is in paradise a tree under the shadow of which a rider can travel for a hundred years and even then he would not be able to cover it.
Abu Sa’id al-Khudri reported that Allah’s Apostle (may peace be upon him) said that Allah would say to the inmates of Paradise: O, Dwellers of Paradise, and they would say in response: At thy service and pleasure, our Lord, the good is in Thy Hand. He (the Lord) would say: Are you well pleased now? They would say: Why should we not be pleased, O Lord, when Thou hast given us what Thou hast not given to any of Thy creatures? He would, however, say: May I not give you (something) even more excellent than that? And they would say: O Lord, what thing can be more excellent than this? And He would say: I shall cause My pleasure to alight upon you and I shall never be afterwards annoyed with you.