Asking Allaah for Taqwa and Purification of the Soul:

Allahumma, ‘aati nafsi taqwaaha, wa zakkihaa Anta khairu man zakkaahaa, Anta Waliyyuhaa wa Maulaaha

O Allah, grant my soul taqwa and purify it, You are the best of those who purify it, You are its Protecting Friend and Guardian/Master.

[Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness (Kitaab ad-dhikr wa duaa wa tawbah wal istighfaar), Hadith 6568]