A group who were overtaken by prayer while traveling, had no water for wudu' despite the rainy weather and a pond by the roadside, but they doubted this

The questioner : A group was overtaken by prayer while traveling and had no water for wudu', and even though the weather was rainy and there was a pond by the roadside, they doubted that this water was not pure, especially since there were workers on the road who were not Muslims. Out of fear that these workers might have used this water, they decided not to use it and performed tayammum, even though the ground was wet and there was no dust. Before the time for prayer ended, they found water. So what is the ruling of the Shari'ah in your view in this case?

The Shaykh : This issue contains several matters:
First: They refrained from using the water out of fear that it might be impure, even though it is water that fell from the sky. Allah the Exalted said: The water that falls from the sky is among the purest of waters; it is purifying and cleanses. The doubt that arose in their minds due to the proximity of the workers, who are not Muslims, is a doubt that does not prevent its use, because the original state is the preservation of its purity. It was obligatory for them to perform wudu' with this water without resorting to tayammum, because if a person doubts the purity or impurity of water, he must base his action on the original state of certainty. If the original state of the water is pure, the doubt regarding its impurity has no effect. If its original state is impure, the original state is its remaining impure. The original state of this water in the pond is purity, so it is pure; indeed, it is purifying and cleanses.
Second: The questioner says that the ground was wet, so they performed tayammum on it, and there was no dust. The answer is that we say: Tayammum on the ground is permissible whether it is wet or dry, whether it is earthy, sandy, or rocky, due to the generality of the saying of Allah the Exalted: And "al-sa'id" (the ground) is everything that rises on the earth. And due to the saying of the Prophet (peace and blessings be upon him): So tayammum on the ground is permissible in whatever state it is in.
Third: This questioner said that they prayed and then found water. If a person performs tayammum and prays while lacking water, and then finds water, even within the time, he does not repeat the prayer, because his conscience is cleared since he did what Allah obligated upon him, which is tayammum when water is absent and prayer. But these people performed tayammum in a state where it was not permissible for them to do so, because it was obligatory for them to purify themselves with the water in the pond.
So the precaution for these people is to repeat the prayer they performed, if they have not already repeated it during that time. Their repetition of it should be in the form in which it was obligatory upon them. So if the prayer was shortened, they repeat it shortened, even if they are in their home country, because the stronger opinion is that whoever repeats a shortened prayer shortens it, and whoever repeats a complete prayer completes it. This is based on the saying of the Prophet (peace and blessings be upon him): His saying (peace and blessings be upon him) "let him pray it" includes performing it in its proper form.