During the battle of Badr, Hazrat Abu Bakr Siddeeq’s (radhiyallahu ‘anhu) son, Hazrat Abdur Rahmaan (radhiyallahu ‘anhu), fought on the side of the disbelievers as he had not yet accepted Islam.
Later, after embracing Islam, whilst seated with his father, Hazrat Abu Bakr Siddeeq (radhiyallahu ‘anhu), he exclaimed, “O my beloved father, during the battle of Badr, you came under my sword a few times. However, considering you being my father, I spared you.”
Hazrat Abu Bakr Siddeeq (radhiyallahu ‘anhu) spontaneously retorted, “Had you come under my sword during the battle, I would have never spared you, as you were fighting against Rasulullah (sallallahu ‘alaihi wasallam).”[1]
[1] تاريخ الخلفاء 1/33