Sayyiduna Ka'b bin Malik (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "When the believer dies, his soul becomes a bird that hangs in the tree of Paradise, until Allah returns it to his body on the Day of Resurrection."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16174