At-Tawba 9:114

As for the prayer of Abraham for his father’s forgiveness, it was only because of a promise he had made to him. However, when it became clear to him that he was an enemy of Allah, he dissociated himself from him[84]. Indeed, Abraham was tender-hearted and forbearing.

[84] This prohibition is not exclusive to Islam as it has been in effect since the time of Abraham (عليه السلام)

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.

114. And Ibrâhîm’s (Abraham) invoking (of Allâh) for his father’s forgiveness was only because of a promise he [Ibrâhîm (Abraham)] had made to him (his father). But when it became clear to him [Ibrâhîm (Abraham)] that he (his father) is an enemy of Allâh, he dissociated himself from him. Verily Ibrâhîm (Abraham) was Awwah (one who invokes Allâh with humility, glorifies Him and remembers Him much) and was forbearing. (Tafsir Al-Qurtubî)[23].

[23] (V.9:114) See the footnote of (V.6:74).

The prayer of Abraham for the forgiveness of his father was only because of a promise he had promised him, but when it had become clear unto him that he (his father) was an enemy to Allah he (Abraham) disowned him. Lo! Abraham was soft of heart, long-suffering.