What should I do when things stick to my foot that prevent water from reaching it, and I cannot remove them except with a substance that I do not possess?

The person performing ablution (wudu') must wash all the parts of the body involved in ablution and not leave out anything, even if it is minor. If there is anything on the foot that prevents water from reaching the skin, it must be removed before ablution. This is indicated by the fact that the Prophet, peace and blessings be upon him, ordered a man to repeat his ablution and prayer because he had left a small unwashed spot (lum'ah) that water did not reach. Similarly, if oil is congealed and prevents water from reaching the skin, it must be removed before ablution. A Muslim should be cautious about their purification and remove anything that prevents water from reaching the parts of the body involved in ablution.