It was narrated that 'Ali said: "I heard a man praying for forgiveness for his parents who were idolaters, and I said: 'Are you praying for forgiveness for them even though they are idolators?" He said: 'Didn't Ibrahim pray for forgiveness for his father?' I went to the Prophet and told him about that, then the following revealed: And Ibrahim's (Abraham) invoking (of Allah) for his father's forgiveness was only because of a promise he (Ibrahim) had made to him (his father)". (Daif)
This hadith also serves as a reminder to be patient with those who do not believe in Allah; just as Prophet Ibrahim was patient with his father despite his disbelief in God's existence. We must remember that everyone has their own beliefs and opinions, and we should respect them regardless of whether or not they agree with ours.