Musnad Ahmad 32:2067

'Affan narrated to us, Sulayman ibn al-Mughirah narrated to us, Thabit narrated to us, from Anas ibn Malik, who said: Harithah, the son of my paternal aunt, went out on the day of Badr with the Messenger of Allah, may Allah bless him and grant him peace, as a young boy looking on; he did not go out for fighting. He said: An arrow struck him and killed him. He said: His mother, my paternal aunt, came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "O Messenger of Allah, my son Harithah—if he is in Paradise, I will be patient and seek reward, but if not, then Allah will see what I shall do." He said: "O mother of Harithah, they are many gardens, and Harithah is in the highest Firdaws."