Dua upon completing ablution — repentance
اللّهُـمَّ اجْعَلنـي مِنَ التَّـوّابينَ وَاجْعَـلْني مِنَ...
اللّهُـمَّ اجْعَلنـي مِنَ التَّـوّابينَ وَاجْعَـلْني مِنَ المتَطَهّـرين
Allahummaj-AAalnee minat-tawwabeena wajAAalnee minal-mutatahhireen
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
Recited after completing ablution.
Source / Reference
At-Tirmithi 1/78