Upon completing the ablution › Wudu & Purification
Dua after ablution — repentance and purity
اللَّهُـمَّ اجْعَـلْنِـي مِنَ التَّـوَّابِيـنَ وَاجْعَـلْنِي مِنَ الْمـتَـطَـهِّـرِين
Allāhummaj`alnī minat-tawwābīna waj`alnī minal-mutaṭahhirīn
Translation
O Allah, make me of those who return to You often in repentance and make me of those who remain clean and pure.
When to recite
Upon completing ablution (wudu).
Source / Reference
Hisnul Muslim 14