اللَّهُمَّ اجْعَلْنِي مِنَ التَّوَّابِينَ وَاجْعَلْنِي مِنَ الْمُتَطَهِّرِينَ
Allahumma-j'alni minat-tawwabina waj'alni minal-mutatahhirin
Ô Allah, fais de moi l'un de ceux qui se repentent et fais de moi l'un de ceux qui se purifient.
Say after completing wudu, following the shahada
This dua asks Allah to make you among those who constantly seek forgiveness and purification.