Hafiz Ibnu Katheer (rahimahullah) has reported on the authority of Ibnu Abi Haatim (rahimahullah) that a strong and powerful person from Syria used to frequent the gathering of Hadhrat Umar (radhiyallahu anhu). When he did not come for some time, Umar (radhiyallahu anhu) enquired about him. Those around replied: “O Ameer-ul-Mu’mineen! He is addicted to wine.” Umar (radhiyallahu anhu) summoned his scribe and ordered him to write (the following letter):From Umar bin Khattab to so and so. Peace be upon you. Before you do I praise Allah whom there is none worthy of worship besides Him, the One who forgives sins and accepts repentance, Who is severe in punishment, the All Mighty. There is none worthy of worship besides Him. To Him is the place of return.
Thereafter, Umar (radhiyallahu anhu) instructed those in his presence to collectively make du`aa for him that his heart accepts this message and that Allah Ta`ala accepts his repentance.When the letter of Umar (radhiyallahu anhu) reached him he read it many times over and pondered over its contents. He then declared that in this I have been warned of punishment and at the same time promised of being forgiven. Thereafter he wept and quit drinking. He made such taubah that he never returned to drinking.
When Umar (radhiyallahu anhu) was informed of this he said to the people: “In such situations you all should adopt the same procedure. You should be concerned to reform him when he is involved in any vice. Make him hopeful of the mercy of Allah Ta`ala and make du`aa to Allah Ta`ala for the acceptance of his taubah. Do not assist Shaitaan against him (by ridiculing and enraging him, thereby causing him to go further away from Deen).” (Tafseer Ibn Katheer, vol. 4, p. 74)