Musnad Ahmad 32:1927

'Affan narrated to us, Hammad—meaning Ibn Salamah—narrated to us, he said: Thabit informed us, from Anas, that Harithah ibn al-Rabi' came on the day of Badr as a spectator, and he was a young boy. An arrow of unknown origin came and struck him in the hollow of his throat, killing him. His mother, al-Rabi', came and said: "O Messenger of Allah, you know my position regarding Harithah. If he is among the people of Paradise, I will be patient; otherwise, Allah will see what I shall do." He said: He replied, "O mother of Harithah, it is not just one Paradise, but many gardens, and he is in the highest Firdaws."