Assalaamu alaykum. I am confused about a statement of Ibn ‘Abbaas that I know that he said. So, please Shaikh, do not send me the other fatwa in which you state that he said it. Ibn ‘Abbaas said that killing a Muslim will not be forgiven. I am confused about why he said this when Allaah says that He forgives all sins, and most scholars say that one can be forgiven for it. Maybe this hadith has something to do with the following:
A’d ibn Ubaidah reported:
“'A man came to Ibn ‘Abbaas and asked, 'Is there repentance for one who kills a believer?' Ibn ‘Abbaas said, 'No, there is nothing but Hellfire.' After the man left, those sitting nearby said to him, 'What is this? You have given us two different judgments, for earlier you judged that whoever killed a believer may have his repentance accepted. What is the matter today?' Ibn ‘Abbaas said, 'Indeed, I suspect he was an angry man intending to kill a believer.' Later, they followed the man and found that it was true.”
Is this hadith authentic, and does it explain what Ibn ‘Abbaas meant by his statement? If not, is Ibn ‘Abbaas' statement authentic? If yes, how do we understand it as to why he said it.

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

The narration on the authority of Ibn ʻAbbaas that is cited in the question, indicates that the repentance of the person who deliberately kills a believer may be accepted. This is one of the two famous opinions reported on the authority of Ibn ʻAbbaas in this regard. The second opinion is that his repentance will not be accepted. The second opinion is supported by the following narration on the authority of Sa'eed ibn Jubayr:

“ʻAbd Ar-Rahmaan ibn Abza commanded me to ask Ibn ʻAbbaas about these two verses: {But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allaah has become angry with him and has cursed him and has prepared for him a great punishment.} [Quran 4:93] and: {And those who do not invoke with Allaah another deity or kill the soul which Allaah has forbidden (to be killed), except by right...} [Quran 25:68] He (Ibn ʻAbbaas) said about the first verse, ‘Nothing has abrogated it.’ And he said about the second verse, ‘This has been revealed in regard to the polytheists.’” [Al-Bukhari and Muslim] This wording was cited in Saheeh Muslim.

Moreover, Saʻeed ibn Mansoor narrated on the authority of Saalim ibn Abu Al-Jaʻd that a man asked Ibn ʻAbbaas, “What do you say about a man who killed a believer intentionally?” He replied, “He shall abide in Hellfire forever.” The man asked, “What do you say if he repented, believed, did well and adhered to guidance?” Ibn ʻAbbaas replied, “From whence will he receive forgiveness? May his mother lose him! I heard your Prophet, sallallaahu ʻalayhi wa sallam, say, ‘On the Day of Judgment, the killer and his victim will be brought, with the slain bleeding and saying, ‘O Lord, ask this one, why did he kill me?’” Ibn ʻAbbaas then recited the verse: {But whoever kills a believer intentionally - his recompense is Hell, wherein he will abide eternally, and Allaah has become angry with him and has cursed him and has prepared for him a great punishment.} [Quran 4:93] He remarked, “Verily, this verse was not abrogated nor (its ruling) replaced, so from where is his repentance?”

The chain of narration of this report was declared authentic by the reviser of the book, Shaykh Dr. Saʻd ibn ʻAbdullaah ibn ʻAbd Al-ʻAzeez Aal Humayd.

The scholars reconciled between the reports on the two scholarly views reported on the authority of Ibn ʻAbbaas regarding the repentance of the one who intentionally kills a Muslim. Perhaps the most correct attempt of reconciliation in this regard is what was stated by Shaykh Ibn ʻUthaymeen in his book Majmoo' Al-Fataawa. He wrote:

“If it is asked, 'What is your opinion regarding the authentically-reported view of Ibn ʻAbbaas that there is no repentance for the killer?' Then there are two possible explanations: Ibn ʻAbbaas may have believed that the repentance of the killer who intentionally commits murder is very unlikely and that he will not be guided by Allaah to repent and accordingly his sin will not be waived and he shall be punished for his crime. Another possible explanation is that Ibn ʻAbbaas meant that there is no repentance for such a killer as far as the right of the victim is concerned because the killer who intentionally murders a person is liable for three rights: the right of Allaah, the right of the victim, and the right of the guardians of the victim (blood heirs).

1- As for the right of Allaah: there is no doubt that (sincere) repentance is sufficient regarding clearing oneself of one's liability from the right of Allaah. He says (what means): {Say: O My servants who have transgressed against themselves (by sinning), do not despair of the mercy of Allaah. Indeed, Allaah forgives all sins...} [Quran 39:53]

This is for the repentant.

2- The right of the murdered person's guardians (blood heirs): it is waived when the murderer surrenders to them and confesses his crime, saying, 'I have intentionally killed so-and-so; do whatever you want to do with me!' They have the right to kill him in retaliation, accept the diyah (blood money), or forgive him.

3- The right of the killed person (victim): there is no way to clear one's liability from this right in the worldly life.

Hence, the view of Ibn ʻAbbaas that there is no repentance for the killer could be interpreted to mean that it is not accepted as far as the right of the victim is concerned.

However, the preponderant view is that if such a killer turns to Allaah in sincere repentance, then even the right of the victim is waived, (however, this does) not (mean) that his right will go lost; rather, Allaah relieves the repentant (killer) from this burden and fulfills the right of the victim Himself, rewarding him with elevating his rank in Paradise or pardoning his sins, because sincere repentance cancels out all sins. This is supported with the general indication of the verse that reads (what means): {...And whoever should do that will meet a penalty. Multiplied for him is the punishment on the Day of Resurrection, and he will abide therein humiliated - except for those who repent, believe and do righteous work. For them Allaah will replace their evil deeds with good. And ever is Allaah Forgiving and Merciful.} [Quran 25:68-70]” [Majmoo' Al-Fataawa]

Allaah knows best.