Praying for the Tawbah of the Sinner

It is reported that ʿAbdullāh b. Masʿūd – Allāh be pleased with him – said:

If you see a man amongst you having committed a sin, do not supplicate Allāh against him and do not revile him; instead, pray to Allāh to cure him and accept his repentance, for when we used to see a man die upon something good, we would have hope for him, and when we used to see a man die upon wrongdoing, we would fear for him.

Ibn Abī Al-Dunyā, Kitāb Al-Tawbah article 112.