Continuity in wudoo’ means not delaying washing one part until the one before it has dried within a moderate amount of time, such as if the part dries because of intense heat or a breeze or by being dried with a towel, for example, if the time taken for drying it does not take too long; what matters is that it should not take too much time.
Some of the scholars describe continuity as meaning that there should not be too much time, as defined by custom, between the washing of various parts of the body, and that is not limited to the time it takes to dry them.
Ibn Qudaamah said in al-Mughni (1/181): The continuity that is required is that one should not leave washing another part of the body until enough time has elapsed for the previous part to dry within a moderate amount of time, because a part may dry quickly at some times and not others. End quote.
It says in Kashf al-Qinaa’ (1/105): Continuity means that one does not delay washing one part until after the part before it has dried at a time when it is neither too hot nor too cold. So one does not delay washing the hands until the face has dried, or delay wiping the head until the hands have dried, or washing the feet until the head has died if it is washed. From this it may be known that if a person delays wiping the head until his face has dried but not his hands, that does not matter. End quote.
Based on this, if a person washes his right foot then dries it, then he washes his left foot without taking as much time as it would ordinarily take for it to dry by itself, then his wudoo’ is valid.
And Allaah knows best.