The souls of the martyrs are within birds that come to the rivers of Paradise

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When your brothers were martyred at Uhud, Allah Almighty placed their souls inside birds which come to the rivers of Paradise, eat of its fruits, and take shelter in lamps of gold hanging in the shade of the Throne. When they found the goodness of their food, their drink and their resting place, they said: Who will convey to our brothers on our behalf that we are alive in Paradise and are being provided for, so that they do not lose interest in jihad and do not turn back in battle? Allah, the Mighty and Majestic, said: I will convey it to them on your behalf. So Allah Almighty revealed this verse: 'And do not think of those who have been killed in the way of Allah as dead; rather, they are alive with their Lord, receiving provision' [Surah Al Imran: 169]."
This hadith is sahih (authentic) on the condition of Muslim, and the two Shaykhs (Bukhari and Muslim) did not record it.

It is narrated from Sayyidah Aishah (may Allah be pleased with her) that she said to Abdullah bin al-Zubayr (may Allah be pleased with them both): "O my nephew! By Allah, your father (Sayyiduna al-Zubayr) and your grandfather (Sayyiduna Abu Bakr al-Siddiq) were certainly among those about whom Allah, the Mighty and Majestic, said: 'Those who responded to Allah and the Messenger after injury had befallen them (at the Battle of Uhud)' [Surah Al Imran: 172]."
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), and they did not record it.