Abdur Rahman bin Ka'b bin Malik (may Allah have mercy on him) said: When the time of death came to Sayyiduna Ka'b bin Malik (may Allah be pleased with him), Umm Bishr bint al-Bara' bin Ma'rur came to him and said: O Abu Abdur Rahman! If you meet my son, convey my greetings of peace to him. Ka'b (may Allah be pleased with him) said: May Allah forgive you, O Umm Bishr! We will be too busy for that. Umm Bishr said: O Abu Abdur Rahman! Did you not hear the Messenger of Allah (peace and blessings be upon him) saying: "Indeed, the souls of the believers are in the bellies of birds that hang from the trees of Paradise"? He said: Of course. Umm Bishr said: Then that is how it is.
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16172