There is no proof that the Prophet (peace and blessings of Allaah be upon him) made any du’aa’ during wudoo’ whilst washing or wiping his limbs etc. Any such du’aa’s that are known are bid’ah (innovation) and have no basis. What is known from Islamic sources is that one should say “Bismillaah il-Rahmaan il-Raheem” at the beginning, and after finishing one should recite the Shahaadatayn and say, “Allaahumma aj’alni min al-tawwaabeen waj’alni min al-mutatahhireen (O Allaah, make me one of those who repent and make me one of those who purify themselves).”
(Fataawa al-Lajnah al-Daa’imah, 5/205)
