اللَّهُمَّ اجْعَلْنِي مِنَ التَّوَّابِينَ، وَاجْعَلْنِي مِنَ الْمُتَطَهِّرِينَ

O Allāh, make me of those who return to You often in repentance and make me of those who remain clean and pure.

Reference: Al-Tirmidhī (#55, 1/78). Also see Ṣaḥīḥ al-Tirmidhī (1/18).