What is the Shar'i ruling for someone who experiences constant and continuous doubt during ablution (wudu') and prayer (salat), and is it obligatory for him to repeat his ablution or prayer in this case?

The questioner must turn away from thoughts of repeating purification and prayer, and cast aside doubts and whisperings, because there is no benefit in performing that about which one doubts as long as the doubt will recur. The فقهاء (jurists) have stated that whoever experiences frequent doubt should cast it aside and not pay attention to it. So, if doubt becomes frequent concerning ablution (وضوء), ritual bath (غسل), removal of impurity (إزالة نجاسة), and dry ablution (تيمم), one should cast it aside.