Musannaf Ibn Abi Shayba 21:774

Abdullah bin Numayr and Abdullah bin Dawud narrated to us, from al-A’mash, from Ibrahim bin al-Muhajir, from Salim bin Abi al-Ja’d, who said: Ali used to say when he finished his ablution: "I bear witness that there is no god but Allah, and I bear witness that Muhammad is His servant and His messenger. My Lord, make me of the repentant and make me of those who purify themselves."