Assalaamu alaykum. I read the narration in Tafseer Ibn Katheer and Al-Qurtubi, who quoted from Tafseer Ibn Abi Hatim and Hilyat-ul-Awliyaa’ that ‘Umar ibn Al-Khattaab wrote a letter to a drunkard and wrote Surah Ghaafir (chapter 40 of the Quran) verses 1-3, due to which that drunkard repented. See the Tafseer (exegesis) of chapter 40, verses 1-3. If that is authentic, I will translate it in English as it is not in the abridged version of Tafseer Ibn Katheer in English

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

This narration was cited by Ibn Katheer when commenting on the verse from Soorah Ghaafir that you referred to. He cited it with its chain of narration on the authority of Ibn Abi Haatim, and it was also cited in Tafseer Ibn Abi Haatim. We did not find any scholar classifying it as Saheeh (authentic) or Dha‘eef (weak/inauthentic).

Apparently – and Allah knows best – there is no harm in citing such narrations to derive lessons therefrom. The scholars are rather lenient with regards to the inauthentic ahaadeeth that are not related to rulings or identifying the lawful and the unlawful, so leniency in relating narrations such as the one you ask about is accepted with greater reason. Therefore, there is no harm in translating the narration in reference.

For more benefit, please refer to fatwas 86128 and 166199.

Allah knows best.