sources mekorot - Wearing clothes backwards or inside out?

As a kid, I was told that if you wear clothing backwards or inside-out then you will forget your Torah learning. What is the source for that claim, and why is that specific outcome tied to that practice?

Answer

There are two statements about clothes that are normally brought together, and are therfore often confused (see here as an example).

1. 
   

   Shulchan Aruch Orach Chaim 2:3 - One should be careful to put on his shirt the right way, and not wear it backwards. The Magen Avraham (S"K 3) explains that (based on Rashi Shabbat 114A) if the disgusting stitches are facing outwards people will see them and he will become disgusting in the eyes of others.

   
   


2. 
   

   The Magen Avraham then quotes Shaar HaKavanot of the Arizal that one should not put on two items of clothes at the same time, as it can make one forget.

   
   

   {for reference, the Shulchan Aruch HaRav and Mishna Berura on this Halacha}

   
   

The Shaar HaKavanot doesn't mention anything about wearing clothes backwards with connection to forgetting. He gives a reason why putting on two garments simultaneously can cause one to forget.

The reason connects physical garments to the spiritual garments of a person, and explains how a person's garments are naturally holy, but by doing sins causes the holy garments to be under the control of the Klipot (forces of impurity). garments surround a person and each garment has a surrounding light (Ohr Makif) that is so high that it cannot be touched by the forces of impurity, thereby shielding the garment itself from the forces of impurity.

When one puts on two garments at once, he leaves no room for the surrounding light between the first and second garment. The garment is therefore vulnerable to Klipot, and Klipot cause forgetfulness, as we know that there is no forgetfulness in the forces of purity and holiness.

Interestingly, it appears from this that there is no problem with putting on two non-overlapping garments (such as both socks or shoes) at once.

The Shulchan Aruch Ha-Ari (S"K 6) explains the same thing in a more simple way.