Imam (a.s) taught his brother Abdullah bin Ali the following dua for seeking forgiveness and mercy. This dua emphasizes repentance, asking Allah for His pardon and compassion.

بِسْمِ اﷲِ الرَّحْمٰنِ الرَّحِیْمِ

Bismillaahir-Rahmaanir-Raheem

In the name of Allah the Beneficent the Merciful.

اَللّٰھُمَّ ارْفَعْ ظَنِّى صَاعِدا، وَلا تُطْمِعْ فِيَّ عَدُوا وَلا حَاسِدا وَاحْفَظْنى قَائِما وَقَاعِدًا، وَيَقْظانا وَ رَاقِدا

Allahumma irfa' dhanni sa'idan, wa la tutmi' fiyya 'aduwwa wa la hasidan, wahfazni qa'iman wa qa'idan, wa yaqdan wa raqidan,

O Allah, raise my expectations of You high, and do not let enemies or enviers deceive me; protect me standing and sitting, awake and asleep.

اَللّٰھُمَّ اغْفِرْ لِی، وَارْحَمْنِي، وَاهْدِنِي سَبِيلَكَ الْأَقْوَمَ، وَقِنَى حَرَّ جَهَنَّمَ وَاحْطُطْ عَنِّى الْمَغْرَمَ وَالْمَأْثَمَ، وَاجْعَلْنِي مِنْ خَيْرِ خِيَارِ الْعَالَمِ.

Allahumma ighfir li, warhamni, wahdini sabilakal aqwam, wa qini harr Jahannam, wa ihtut 'anni al-maghram wal-ma'tham, waj'alni min khairi khiyar al-'alam.

O Allah, forgive me, have mercy on me, guide me to Your straight path, shield me from the heat of Hellfire, absolve me from debts and sins, and make me among the best of the best in the world.