From his father that the Messenger of Allah (ﷺ) said: "The souls of the martyrs are in green birds, suspended from the fruit of Paradise, or the trees of Paradise."

This Hadith is Hasan Sahih.
Jami` at-Tirmidhi Book 22, Hadith 24
← Previous Hadith That the Messenger of Allah (ﷺ) said: "Dying in the cause of Allah expiates every sin." Jibril said: "Except for debt." So the Messenger of Allah (ﷺ) said: "Except the debt."

There are narrations on this topic from Ka'b bin 'Ujrah, Jabir, Abu Hurairah, and Abu Qatadah. This Hadith is Gharib, we do not know of it as a Hadith of Abu Bakr (a narrator) except from this Shaikh (Yahya bin Talhah)

He said: I asked Muhammad bin Isma'il about this Hadith and he did not know it. He said: "I think that he intended the Hadith of Humaid, from Anas, from the Prophet (ﷺ) that he said: 'There is none from the people of Paradise who would like to return to the world except for the martyr.'"

Jami` at-Tirmidhi Book 22, Hadith 23 Next Hadith → That the Messenger of Allah (ﷺ) said, "I was shown the first of (every) three to enter Paradise: A martyr, an 'Atif, who is a Muta'affif, and a slave who perfected his worship of Allah, and was sincere to his masters."

This Hadith is Hasan.

Jami` at-Tirmidhi Book 22, Hadith 25