When Mordechai hears of the plot against the Jewish people, he displays his sadness by appearing בִּלְב֥וּשׁ שָֽׂק, bilvush sock Esther 4:2.
What is the halachic source that appearing with a sock denotes mourning? Is it that wearing only one sock points to loss? Is it about a lack of shoes?
David HaMelech said of this practice (Tehillim 30:12):
הפכת מספידי למחול לי פתחת שקי ותאזרני שמחה
You turned my mourning into dancing for me, you removed my socks and girded me with happiness.
So we see that it’s not simply not wearing shoes, but actively wearing socks that indicates mourning. (Perhaps the common custom nowadays to wear socks under our shoes is meant to be a sign of mourning the Beis HaMikdash.)
What is the reason for this? David HaMelech says further in Tehillim 147:9:
נוֹתֵ֣ן לִבְהֵמָ֣ה לַחְמָ֑הּ לִבְנֵ֥י עֹ֝רֵ֗ב אֲשֶׁ֣ר יִקְרָֽאוּ׃
Who gives to an animal its bread, to young ravens when they call out?
Who, indeed, is it who gives food to young ravens? It must be the Angel of Death, who smites creatures, which the ravens then eat.
“Bread,” of course, is a euphemism for living creatures; as we find in Bereishis 39:6:
הַלֶּ֖חֶם אֲשֶׁר־ה֣וּא אוֹכֵ֑ל
The bread which he eats
which, as Rashi explains,
הִיא אִשְׁתּוֹ
This is [Potiphar’s] wife
Rashi further notes on Bereishis 37:33:
חיה רעה אכלתהו. [...] סוֹפוֹ שֶׁתִּתְגָּרֶה בוֹ אֵשֶׁת פּוֹטִיפַר.
”A wild animal ate him” - [...] His end is that the wife of Potiphar will drag him.
So we see that Potifar’s wife is a wild animal, and she is called “bread,” so we may deduce that living creatures in general are called “bread.”
Okay, back to the passuk in Tehillim 147. Having established that we’re talking about the Angel of Death, the passuk continues (v. 10):
לֹ֤א בִגְבוּרַ֣ת הַסּ֣וּס יֶחְפָּ֑ץ לֹֽא־בְשׁוֹקֵ֖י הָאִ֣ישׁ יִרְצֶֽה׃
Not in the strength of a horse does he desire, nor in the shins of man is he appeased.
The Angel of Death doesn’t desire strength, so the practice is to mourn and refrain from many activities. He is not appeased by the shins of man, so the practice is to cover them with socks.
You ask a hole-y question. This has nothing to do with or the lack of shoes. It means a complete outfit made out of Sock. By wearing an outfit that smells to the high heavens, people will come to turn to heaven and beg for redemption. (Source: Pitachta Saki - Esther 4:2)
My oh my ... I really do need to get you my book, "Socks in the City" when I publish it!
You asked " Is it that wearing only one sock points to loss?" Of course it does! You mean to tell me that you've never lost one sock in the machine? Forget about you looking foolish with all those single socks in your sock drawer. (If you read my book, I explain exactly where the socks go.) But, how do you think the sock feels without its spouse? It suffers a tremendous loss!
A lost sock is like a cold foot crying for warmth! It's one thing to get cold feet, because at least you can run into a warm room. But, a single cold foot? One with a sock and one without?? Well, I'll let you figure what a sad day that is esp. when you can't really run and hide from others laughing at you.
So, suffice to say that there are two things that mourn. The sock for losing its spouse, and you for having to look like a cold-footed nebbish.
