The Repentance - 9:114
The only reason Abraham asked forgiveness for his father was because he had promised it to him beforehand. When it became clear to him that he was an enemy of Allah, he turned away from him. Ibrahim was very sensitive and very compassionate.
Prophet Abraham promised to ask forgiveness for his father:
Mary/19:41
Remember Abraham in the Book; he was a prophet, a truthful one.
Mary/19:42
"He said to his father, "My father, why do you serve that which does not hear or see or benefit you?"
Mary/19:43
My father, a knowledge has come to me which has not come to you. Follow me and I will guide you to a straight path.
Mary/19:44
My father, do not serve Satan. Satan has opposed the Most Merciful.
Mary/19:45
My father, I fear that you may be punished by the Most Merciful and that you may be a friend of Satan.
Mary/19:46
"(His father said:) "Are you turning away from my gods, Abraham? If you do not stop this, I will stone you, go away from me!"
Mary/19:47
"Peace be upon you,"he said, "I will beg my Lord for your forgiveness; He is most merciful to me."
Mary/19:48
I am leaving you and those whom you call upon besides Allah, I call upon my Lord, and I hope that I will not be unfortunate in calling upon my Lord.
The Poets/26:84
Make me a good example for the generations to come.
The Poets/26:85
Make me of those who inherit Paradise of Blessings.
The Poets/26:86
Forgive my father, for he has gone astray.