It is reported that a man was closely watching Bishr As-Sulaimi (radhiAllahu anhu), who was prolonging his prayer and performing it well.
When Bishr completed his prayer, he said to the man, “Do not be deceived by what you have seen from me. For indeed, Iblis the Devil – may Allah curse him – worshipped Allah for thousands of years and then ended up being what he is now!”
Source : Bahrud-Dumu, pg. 171, “Glimpses of the Lives of Righteous People” – by Majdi Muhammad Ash-Shahawi