Once I performed Wudhoo’ (ablution) for prayer and when I was drying my foot before starting the prayer, there was a black spot at the tip of my toe on my toenail from the outside. It was as small as a lentil in size. I tried to remove it with my hand but did not exert my utmost and it was not removed. I thought it was a spot of blood under the skin or something like that. I ignored the matter and performed the prayer. Three days later I did not find that spot as if it disappeared all of a sudden. Now I am doubtful whether it was something preventing the water from reaching the skin or it was just a spot of blood under the skin. Being doubtful about the nature of this spot, am I required to repeat the prayers of the three days? I usually find small spots on my skin and therefore I repeat the prayer. What should I do? Thank you.

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

If you were sure or most likely believed that there was a spot on your foot before performing Wudhoo’, you were required to remove it or at least save no effort to remove it if the spot was on the external part of the skin and had a mass, so that you would be sure that water had reached the skin or you saved no effort to do so as much as you could. It is one of the prerequisites of Wudhoo’ that water reaches all the parts of the Wudhoo’ organs that must be washed. When one is not certain that the prerequisites of Wudhoo’ are fulfilled and he performs the prayer with that Wudhoo’, then the prayer is invalid. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Allaah does not accept the prayer of a person who is in a state of (minor) impurity unless he performs Wudhoo’." [Al-Bukhari]

It is one of the Islamic principles that one is not absolved of liability unless he is certain of performing the act of worship validly, with all the prerequisites fulfilled. Consequently, we are of the view that you have to repeat the prayers that you performed with that Wudhoo’ where the relevant prerequisites were not achieved.

The same ruling is applied to a person who performs the prayer while there are thick spots on his nails which prevent water from reaching the skin. One is required to repeat the prayer after removing these spots, and even repeat Wudhoo’ according to some scholars. It is narrated that the Prophet, sallallaahu ‘alayhi wa sallam, saw a man praying and there was an unwashed spot on the back of his foot that had not been reached by water, and he (the Prophet) commanded that man to repeat both Wudhoo’ and prayer. [Abu Daawood; Al-Albani: authentic]

We advise the questioner to take care of his purification and save no effort to do so perfectly. Meanwhile, we alert him to avoid obsessions and not to give them free rein. 

Allaah Knows best.