Sayyiduna Ka'b bin Malik (may Allah be pleased with him) used to narrate that the Messenger of Allah (peace and blessings be upon him) said: "The soul of the believer is only a bird that hangs in the trees of Paradise, until Allah returns it to its body on the day He resurrects him."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16171