The Prophet ﷺ said: When your brethren were smitten at the battle of Uhud, Allah put their spirits in the crops of green birds which go down to the rivers of Paradise, eat its fruit and nestle in lamps of gold in the shade of the Throne. Then when they experienced the sweetness of their food, drink and rest, they asked: Who will tell our brethren about us that we are alive in Paradise provided with provision, in order that they might not be disinterested in jihad and recoil in war? Allah Most High said: I shall tell them about you; so Allah sent down; "And do not consider those who have been killed in Allah's path." till the end of the verse. (Using translation from Abū Dāʾūd 2520)
قَالَ رَسُولُ اللهِ ﷺ لَمَّا أُصِيبَ إِخْوَانُكُمْ بِأُحُدٍ جَعَلَ اللهُ ﷻ أَرْوَاحَهُمْ فِي أَجْوَافِ طَيْرٍ خُضْرٍ تَرِدُ أَنْهَارَ الْجَنَّةِ تَأْكُلُ مِنْ ثِمَارِهَا وَتَأْوِي إِلَى قَنَادِيلَ مِنْ ذَهَبٍ فِي ظِلِّ الْعَرْشِ فَلَمَّا وَجَدُوا طِيبَ مَشْرَبِهِمْ وَمَأْكَلِهِمْ وَحُسْنَ مَقِيلِهِمْ قَالُوا يَا لَيْتَ إِخْوَانَنَا يَعْلَمُونَ بِمَا صَنَعَ اللهُ لَنَا لِئَلا يَزْهَدُوا فِي الْجِهَادِ وَلا يَنْكُلُوا عَنِ الْحَرْبِ فَقَالَ اللهُ ﷻ أَنَا أُبَلِّغُهُمْ عَنْكُمْ فَأَنْزَلَ اللهُ ﷻ هَؤُلاءِ الْآيَاتِ عَلَى رَسُولِهِ {وَلَا تَحْسَبَنَّ الَّذِينَ قُتِلُوا} [آل عمران 169]