«والشرط: ما لا يتم الشيء إلا به، ولا يكون داخلا في ماهيته»
A shart is something without which an act cannot be completed, yet it is not part of the act’s essence.
Wudu is a condition for valid prayer; it is not one of the prayer’s internal acts, but prayer requires it.
The existence of a condition does not itself establish that the act has been performed. Wudu makes prayer possible in the relevant respect; actual performance is another matter.