The Messenger of Allah ﷺ said, "The souls of the martyrs reside in green birds that feed from the fruits of Paradise," or "the trees of Paradise."
حدثنا ابن أبي عمر حدثنا سفيان بن عيينة عن عمرو بن دينار عن الزهري
أن رسول الله ﷺ قال إن أرواح الشهداء في طير خضر تعلق من ثمر الجنة أو شجر الجنة
[Its chain is daif] Ibn Majah also recorded it in the Book of Zuhd, chapter on mentioning the grave and decay, no. 4271, and Nasai: /10, no. 2075, from the hadith of Zuhri through this same route. Zuhri's teacher, Abdul-Rahman bin Abdullah bin Kaab, did not hear this hadith from his grandfather. Refer to Nihayah with my verification, no. 1637. Ibn Hibban graded it sahih, no. 734, and it is found in Muwatta: 1/240, no. 569. It has a corroborating narration in Ahmad: 424/6, 425, no. 27931, though its chain is daif.