Supplication after completing ablution

أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ وَأَشْهَدُ أَنَّ مُحَمَّداً عَبْدُهُ وَرَسُولُهُ

(I bear witness that none has the right to be worshipped except Allah, alone without partner, and I bear witness that Muhammad is His slave and Messenger.)

Source: Muslim 1/209.

اللَّهُمَّ اجْعَلْنِي مِنَ التَّوَّابِينَ وَاجْعَلْنِي مِنَ الْمُتَطَهِّرِينَ

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

Source: At-Tirmizi 1/78, Al-Albani, Sahih At-Tirmizi 1/18

سُبْحانَكَ اللَّهُمَّ وَبِحَمْدِكَ, أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ أَنْتَ, أَسْتَغْفِرُكَ وَأَتوبُ إِلَيْكَ

(How perfect You are O Allah, and I praise You. I bear witness that None has the right to be worshipped except You. I seek Your forgiveness and turn to You in repentance.)

Source: An-Nasa'i, 'Amalul-Yawm wal-Laylah, p. 173, Al-Albani, 'Irwa'ul-Ghalil 1/135, 2/94.