At-Tawbah 9:114

Wama kana istighfaruibraheema li-abeehi illa AAan mawAAidatin waAAadahaiyyahu falamma tabayyana lahu annahu AAaduwwun lillahitabarraa minhu inna ibraheema laawwahun haleem

And the request of forgiveness of Abraham for his father was only because of a promise he had made to him. But when it became apparent to him [i.e., Abraham] that he [i.e., the father] was an enemy to Allāh, he disassociated himself from him. Indeed was Abraham compassionate and patient.

As for the prayer of Ibrāhīm for the forgiveness of his father, it was only due to a promise he had made to him. Later, when it became clear to him that he was an enemy of Allah, he withdrew himself from him. Indeed, Ibrāhīm was very tender-hearted, very forbearing.