It is not good to allow doubts to be your habit, for it may turn into a chronic psychological disease or even worse. Excessive doubting is actually one of Satan’s ways to make man discard his obligations and neglect acts of worship. Therefore, man should not give Satan the opportunity to intervene in his relationship with Allah and spoil it. So, if your doubts concerning wudu’ and prayers have become something chronic that you cannot overcome, you do not have to make up your prayer unless you are sure that you did something wrong while praying. In doing so, you will gradually give up such kind of doubts, Allah willing. Allah Almighty says: “Allah burdens no soul beyond what it can bear.” (Al-Baqarah: 286). As for how to get rid of this, we should continue reciting the Glorious Qur’an and pray to Allah to help you to overcome this problem. Dhikr (remembrance of Allah) is highly needed and also helpful in this matter. This is based on the Qur’anic verse: “Who have believed and whose hearts have rest in the remembrance of Allah. Verily in the remembrance of Allah do hearts find rest!” (Ar-Ra`d: 28)
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: “This situation is clearly due to the whisperings of Satan. He is definitely trying to cast doubts in regards to the validity of your ablution and prayer in order to make you give up your religious practices. So you need to exercise vigilance and not allow yourself to give in to such whisperings.
The Prophet (peace and blessings be upon him) advised us that when faced with such situation, first of all, we must seek refuge in Allah by saying “‘a`dhu billahi mina ash-shaytani ar-rajeem (I seek refuge in Allah from the Satan, the accursed)”. And secondly you simply formulate the intention and perform the wudu’ or prayer once, trying to concentrate by pondering the meanings of what you are reading and never pay any attention to any such whisperings. Your wudu’ and prayer are perfectly valid.
Finally, consistently pray to Allah to help you to overcome such Satanic whisperings. You may read one of these Qur’anic supplications: “O Lord, I seek refuge in You from whisperings of the devils, and I seek refuge in You from them being present around me.” (Al-Mu’minun: 97-98)
You can also make use of the following supplication: “Allahumma inni ‘a`udhu bika mina shaki wannifaq walkufri wa fujoor (O Allah, I seek refuge in You from doubts, hypocrisy, disbelief and immoral conduct.)'”
The well-known Muslim scholar, Sheikh Sa`d Al-Humayd, adds: “Muslims always have to take the easier option always, and do not think about the sin or punishment. For instance, in a prayer, when you are not sure whether you have prayed three or four rak`ahs, you have to assume that it is four, and the part of the body which you are unsure whether you have washed it, you have to assume that you have washed it. This applies to every situation you face: take the easier option. If you do that, you will defeat the Satan who has subjected you to this overwhelming waswasah.”
Sheikh M. S. Al-Munajjid, a prominent Saudi Muslim lecturer and author, points out:
“If a person knows without doubt that wind has passed, then he should leave the prayer. However, if he is in doubt but is not certain, then he should not leave unless he becomes certain — by hearing the wind pass or smelling it. If he finds that he has passed wind, he should leave; otherwise he should pay no attention to it. Abu Hurayrah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: “If one is in prayer and feels movement in his behind, (and is in question whether) he has passed wind or not, and he is in doubt, then he should not leave unless he hears the sound or detects the smell.” (Reported by Abu Dawud)”