Right Way To Do Wuzu And Washing Limbs Four Times
Prophet (sws) was pointing towards the fact that adding or removing anything intentionally from the prescribed Wuzu will be a sin because if that additional thing is done or something is removed from Wuzu intentionally as part of religion, then it is as good as starting a Biddah in religion and this is exactly how Biddah starts. This is not related to someone who unintentionally washes face or arm four times . Following narration depicts a better picture: https://sunnah.com/abudawud:135