Can he wipe over his socks if he put the right sock on before washing his left foot?

It is better and is more on the safe side for the person doing wudoo’ not to put on his socks until he has washed his left foot, because the Prophet (peace and blessings of Allaah be upon him) said: “When one of you does wudoo’ and puts on his khuffayn, he may wipe over them and pray in them, and he need not take them off if he does not want to, except in the case of janaabah.” Narrated from Anas (may Allaah be pleased with him) by al-Daaraqutni and by al-Haakim who classed it as saheeh. 

It was narrated from Abu Bakrah al-Thaqafi (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) granted a dispensation to the traveller for three days and three nights, and to the non-traveller for one day and one night: if he purifies himself and puts on his khuffayn (leather slippers or socks), he may wipe over them. Narrated by al-Daaraqutni and classed as saheeh by Ibn Khuzaymah. 

It is narrated in al-Saheehayn from al-Mugheerah ibn Shu’bah (may Allaah be pleased with him) that he saw the Prophet (peace and blessings of Allaah be upon him) doing wudoo’ and he wanted to take off his khuffayn. The Prophet (peace and blessings of Allaah be upon him) said to him: “Leave them, for I put them on when they (my feet) were in a state of purity.” 

The apparent meaning of these three ahaadeeth and similar reports is that it is not permissible for a Muslim to wipe over his khuffayn except when he put them on in a state of full purity. The one who puts his khuff or sock onto his right foot before washing his left foot is not in a state of full purity. 

Some scholars are of the view that it is permissible to wipe over the sock even if the person put his right foot into the khuff or sock before washing his left foot, because in each case it is done after washing the foot. 

But the first view is more on the safe side, and it is more apparent based on the evidence. So the person who has done that should take off the khuff or sock from his right foot before wiping, and put the sock back on after washing the left foot, so that he avoids an area of scholarly dispute and will be on the safe side with regard to his religious commitment. End quote. 

Shaykh Ibn Baaz (may Allaah have mercy on him). 

Majmoo’ Fataawa Ibn Baaz, 10/116 

Another indication that it is not permissible to wipe over the khuffayn unless one put them on when in a state of full purity is the report narrated by Ibn Khuzaymah and al-Daaraqutni from Abu Bakrah (may Allaah be pleased with him), according to which the Prophet (peace and blessings of Allaah be upon him) granted a concession to the traveller for three days and nights, and to the non-traveller for one day and night, allowing them to wipe over the khuffayn if they put them on after purifying themselves. Classed as saheeh by al-Khattaabi. Al-Bayhaqi narrated that al-Shaafa’i classed it as saheeh and al-Nawawi classed it as hasan. Talkhees al-Habeer, 1/278. 

See al-Majmoo’ by al-Nawawi, 1/541.