The addition of the word “kareem” in the du‘aa’ of Laylat al-Qadr is not proven
Question

It is quoted in Saheeh at-Tirmidhi by Shaykh al-Albaani (may Allah have mercy on him):
3513: Qutaybah told us: Ja‘far ibn Sulaymaan ad-Dab‘i told us, from Kahmas ibn al-Hasan, from ‘Abdullah ibn Buraydah, from ‘Aa’ishah, who said: I said: O Messenger of Allah, if I realise when it is Laylat al-Qadr, what do you think I should say? He said: “Say: Allahumma innaka ‘Awfuwwun Kareem, tubhibb al-‘afwa, fa‘fu ‘anni (O Allah, You are forgiving and most generous, You love forgiveness, so forgive me).” The shaykh (may Allah have mercy on him) deemed it to be saheeh. But the same hadith was narrated by Ibn Maajah (3850) and in as-Silsilah as-Saheehah, Shaykh al-Albaani stated that the additional word “Kareem (most generous)” was added by one of the scribes. Did the shaykh fail to notice the additional word “kareem” in Saheeh at-Tirmidhi, or is it saheeh in his opinion? If it is not proven in his opinion, then why did he not point out in Saheeh at-Tirmidhi that it is something that has been added?
Praise be to Allah.Shaykh al-Albaani (may Allah have mercy on him) was a scholar and critic of hadith who examined the reports and tried his best in doing so, but he was vulnerable to forgetfulness and error, like other scholars, and that does not detract from his standing in the slightest; rather he will be rewarded for that, by Allah’s leave, receiving a single reward. That is by the grace and kindness of Allah, may He be exalted, to the scholars and fuqaha’; He grants them a single reward for their mistakes, and grants them a double reward for what they get right. What matters is that researchers and seekers of knowledge follow the correct methodology in research and do not follow blindly; the status of a scholar does not prevent them from reviewing the evidence and conducting their own research, for academic research should be objective and neutral, and should only be based on real research and examination, and it should not be restricted to some particular names of great scholars, no matter how well versed and prominent they may be.
Therefore we may say that Shaykh al-Albaani (may Allah have mercy on him) failed to point out the erroneous addition of the word “kareem” in the hadith about the du‘aa’ of Laylat al-Qadr, as the hadith was narrated via many chains of narration, and it was narrated by the authors of Jaami‘s, Sunans and Musnads, and not one of them mentioned this extra word “kareem”; rather all of them narrated the well-known version of the du‘aa’: “Allahumma innaka ‘Awfuwwun, tubhibb al-‘afwa, fa‘fu ‘anni (O Allah, You are forgiving, You love forgiveness, so forgive me).”
But this mistake occurred in al-Albaani’s book Saheeh at-Tirmidhi (no. 3513) only.
With regard to his book Silsilat al-Ahaadeeth as-Saheehah – concerning which researchers are agreed that the research that was put into it was more precise and deeper than that of his other books, Saheeh as-Sunan and Da‘eef as-Sunan – the shaykh pointed out this erroneous addition and said:
In Sunan at-Tirmidhi after the word “ ‘Afuw” there appears this additional word “Kareem”, for which there is no basis in the earlier sources or any other sources that were narrated from the earlier sources. What appears to be the case is that it is something that was inserted by one of the scribes or modern typists. It does not appear in the Indian edition of Sunan at-Tirmidhi on which al-Mubaarakfoori’s commentary, Tuhfat al-Ahwadhi (4/264), was based, or in other editions.
What supports that is the fact that in some of his reports, an-Nasaa’i narrated it via the same isnaad as at-Tirmidhi, as both of them narrated it from their shaykh, Qutaybah ibn Sa‘eed, without this addition.
This addition also appears in an essay by our brother ‘Ali al-Halabi, entitled Muhadhdhab ‘Amal al-Yawm wa’l-Laylah li Ibn as-Sunni (no. 202), but it is not narrated by as-Sunni, because he narrated from his shaykh, an-Nasaa’i – as stated above – from Qutaybah, but he attributed it to at-Tirmidhi and others. What would have been more appropriate is to put this word between brackets, as is the practice nowadays, to highlight the fact that it was only mentioned by at-Tirmidhi. To be accurate, however, this word should not be mentioned at all except to point out that it has no basis.
End quote from Silsilat al-Ahaadeeth as-Saheehah (13/140).
Hence some researchers regard al-Albaani’s comment here, in Silsilat al-Ahaadeeth as-Saheehah – as constituting a clear retraction of his having regarded this addition as sound in Saheeh at-Tirmidhi.
Whatever the case, whether you call it retraction or a conclusion that is separate from the first conclusion, what matters is that he stated the correct view and corrected the mistake.
What is most likely to be the case is that this extra word, with which people are familiar, was taken from some editions of the books of hadith, not from the reports of the hadith itself, meaning that the scholars who narrated the hadith with this extra word “kareem” only did so because they found some manuscripts that contained the extra word “kareem”, as the commentators said concerning the Mu’sasat ar-Risaalah edition of Musnad al-Imam Ahmad (42/236): In “Q” it says “ ‘Afuwwun kareem.” End quote. “Q” is a symbol referring to a particular manuscript to which they referred. See their Introduction (1/104). Similarly, with regard to the al-Maknaz edition (11/6118, no. 26021), the commentators said: In “Q” it says “ ‘Afuwwun kareem.”
Hence many scholars transmitted the hadith with this additional word in their books, such as: Ibn al-Atheer in Jaami‘ al-Usool (4/324); al-‘Imraani in al-Bayaan fi’l-Madhhab ash-Shaafa‘i (3/568); al-Khaazin in Lubaab at-Ta’weel fi Ma‘aani at-Tanzeel (4/452); Ibn al-Qayyim in Badaa’i‘ al-Fawaa’id (2/143); al-Khateeb ash-Sharbeeni in al-Iqnaa‘ fi Hall Alfaaz Abi Shujaa‘ (1/274); al-Ameer as-San‘aani in at-Tahbeer li Eedaah Ma‘aani at-Tayseer (4/268); at-Tahtaawi in Haashiyat ‘ala Maraaqi al-Falaah Sharh Noor al-Eedaah (p. 401).
All of them narrated the hadith with the additional word “kareem” and without mentioning any isnaad. Some of them attributed it to Sunan at-Tirmidhi. This is assuming that the manuscripts were copied accurately.
But today we have no doubt that this additional word is not part of the original text of the hadith, because dozens of books of hadith mentioned the text of this hadith without this additional word. We referred to editions that were checked against many manuscripts of Sunan at-Tirmidhi, and we did not find any reference to this additional word, such as the edition annotated by Bashaar ‘Awaad (5/490), and another edition annotated by Shu‘ayb al-Arna’oot (6/119).
And Allah knows best.