Upon completing the ablution

'Ash-hadu 'an lā 'ilāha 'illallāhu waḥdahu lā sharīka lahu wa 'ash-hadu 'anna Muḥammadan `abduhu wa Rasūluhu. I bear witness that none has the right to be worshipped but Allah alone, Who has no partner; and I bear witness that Muhammad is His slave and His Messenger. Reference: Muslim 1/209.
Allāhummaj`alnī minat-tawwābīna waj`alnī minal-mutaṭahhirīn. O Allah, make me among those who turn to You in repentance, and make me among those who are purified. Reference: At-Tirmidhi 1/78. See also Al-Albani, Sahih At- Tirmidhi 1/18
Subḥānaka Allāhumma wa biḥamdika, 'ash-hadu 'an lā 'ilāha 'illā 'Anta, 'astaghfiruka wa 'atūbu 'ilayk. Glory is to You, O Allah, and praise; I bear witness that there is none worthy of worship but You. I seek Your forgiveness and turn to You in repentance. Reference: An-Nasa'i, 'Amalul-Yawm wal-Laylah, p. 173. See also Al-Albani, 'Irwa'ul-Ghalil 1/135 and 2/94.