The ruling on one who performed tayammum and then found water before the time for prayer ended

Q: A group of people were overtaken by the time for prayer while they were traveling. They had no water for wudu, and although it was raining and there was a ditch alongside the road, they were concerned that this water was not pure, especially since there were non-Muslim workers working on the road; they feared that these workers might have used the water on the road. So they decided not to use the water and performed tayammum, even though the ground was wet and there was no dust. Before the time for prayer ended, they found water. What is the ruling in the situation as described?

A: It is obligatory for the people you mentioned and those similar to them to perform wudu with the available water if wudu can be performed with it; because the original state of water is purity, just as the original state is the obligation of wudu and the impermissibility of tayammum except in cases of inability to perform wudu. However, if the water is not suitable for wudu due to its small quantity, or because it is mixed with earth to the extent that it becomes like mud rather than water, then tayammum is sufficient for them.
They must also seek out earth by removing the crust on the surface of the ground if the rain was light. If the rain was heavy and had soaked into the ground, tayammum on dry earth, or on any of their belongings that have dust on them, is sufficient for them; for Allah (Glorified and Exalted is He) said: : [Surat al-Taghabun: 16].
If they find water after the prayer, they do not have to repeat it; because there is a report in the Sunnah indicating this, provided they did not act negligently.