The Messenger of Allah ﷺ said, "Allah will say to the people of Paradise, 'People of Paradise!'They will reply, 'Here we are, our Lord, at Your service.'He will ask, 'Are you content?'They will answer, 'How could we not be content, when You have given us what You have given to no one else among Your creation?'He will say, 'I shall give you something better than that.'They will ask, 'Our Lord, what could be better than that?'He will reply, 'I shall bestow My pleasure upon you, and I shall never be displeased with you after it.'"
قال رسول الله ﷺ: إن الله يقول لأهل الجنة: يا أهل الجنة! يقولون: لبيك ربنا وسعديك. فيقول: هل رضيتم؟ فيقولون: وما لنا لا نرضى، وقد أعطيتنا ما لم تعط أحدا من خلقك. فيقول: أنا أعطيكم أفضل من ذلك. قالوا: يا رب! وأي شيء أفضل من ذلك؟ فيقول: أحل عليكم رضواني، فلا أسخط عليكم بعده أبدا.
Bukhari narrated it in the Chapter on Softening of Hearts (6549), and Muslim in the Chapter on Paradise, its Bliss, and its People (2829), both through Malik bin Anas, from Zayd bin Aslam, from Ata bin Yasar, from Abu Saeed Khudri, who said, then he mentioned it. The wording given here is Bukhari's, and Muslim's wording is similar.