If a person is wearing two layers of khufoof or socks, which one should he wipe over?
Question

                Is it permissible to wipe over two layers of socks worn one over another? If that is permissible and a person wipes over them, then takes off one layer and then breaks his wudoo’, is it permissible for him to wipe over the other or not?.
Praise be to Allah.
    It is permissible for a person to wear two layers of khufoof 
    or socks. If he wipes over one – in cases where it is permissible to do so, 
    as we shall see below – then he takes one off, and breaks his wudoo’, it is 
    permissible for him to wipe over the other, according to the opinion of some 
    of the scholars. 

    Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) a number 
    of scenarios in which a person wears two layers of khufoof or socks, as 
    follows: 

    1 – If a person put on socks or khufoof then broke his 
    wudoo’, then put on another pair before doing wudoo’, the ruling applies to 
    the first layer, i.e., if he wants to wipe over them after that, he has to 
    wipe over the first layer, and it is not permissible for him to wipe over 
    the second layer. 

    2 – If he puts on socks or khufoof, then he breaks his wudoo’ 
    and wipes over them, then he puts on a second layer, then he may wipe over 
    the second layer according to the sound view. It says in al-Furoo’: 
    That is permissible according to Maalik. End quote. Al-Nawawi said: This is 
    the best view, because he put them on in a state of purity (tahaarah), and 
    their view that it is a lesser kind of purity is not acceptable. End quote. 

    If we accept that, then the period of wiping starts from the 
    first time he wiped over the first layer. 

    In this case he may also wipe over the first layer, without a 
    doubt. 

    3 – If he puts khufoof on over khufoof or socks, and he wipes 
    the outer layer then takes it off, can he wipe over the lower layer for the 
    remainder of the period? I did not see any clear statement on this, but 
    al-Nawawi stated that Abu’l-‘Abbaas ibn Surayj said that if he puts 
    overshoes over the khufoof then one of three scenarios must apply: one of 
    which is that they become like a single khuff, with the upper layer visible 
    and the second layer like a lining, therefore he may wipe over the lower 
    layer until the period for wiping ends from the time he wiped over the upper 
    layer, which is like the case when the outer surface of the khuff becomes 
    worn or scratched – it is permissible to wipe over the lining.” End quote 
    from Fataawa al-Tahaarah, p. 192 

    The “overshoe” (jurmooq) is something that is worn over the 
    regular khufoof, especially in cold countries. 

    Kashshaaf al-Qinaa’, 1/130 

    Al-Sharh al-Mumti’, 1/211 

    And Allaah knows best.