Yeshayahu's fulfillment of Hashem's command took place in a vision and was not witnessed by the public. As such, the message of the prophecy may not have been meant for the people of Yehudah. Instead, this prophecy was meant for Yeshayahu himself as part of his series of of נבואות הגוים.
וּפִתַּחְתָּ הַשַּׂק מֵעַל מׇתְנֶיךָ וְנַעַלְךָ תַחֲלֹץ מֵעַל רַגְלֶךָ – Hashem indeed asked Yeshayahu to untie and remove his sackcloth and shoes. However, this was only in a dream.
עָרוֹם וְיָחֵף – These commentators assert עָרוֹם וְיָחֵף means completely unclothed and barefoot.
שָׁלֹשׁ שָׁנִים – Ibn Ezra writes that the שָׁלֹשׁ שָׁנִים refers to the latter part of the verse. Egypt and in Cush will be destroyed three years after this prophecy. Radak explains that the vision in reality took just a moment. It seemed, to Yeshayahu, however, as if it took three years
Standards for prophets? This approach successfully neutralizes this issue by assuming everything was in a prophetic vision and not in public.
Ibn EzraYeshayahu 20About R. Avraham ibn Ezra and RadakYeshayahu 20About R. David Kimchi read this as referring to the residents of the Land of Israel who, while at war with the Assyrians, are placing their trust in Egypt. When Egypt and Cush will be destroyed, these Israelites will be ashamed of having counted on those other nations.This account perhaps highlights the intensity of Egypt's destruction.
Goal of the Prophecy – According to this approach, the prophecy is not meant for the Judeans living in the Land of Israel. Rather, this prophecy is solely meant to tell of the Egyptian demise by the hands of the Assyrians.1 A coincidental result of such a demise will be the shame of the Israelites in that they put there trust in Egypt.
Purpose of the שק and its removal
Historical Context
Public Action
As per the simple meaning of the text, Yeshayahu's action was performed in the real world and not in a private vision with Hashem. As such whatever message Yeshayahu intends to transmit will most likely be impressed on the Kingdom of Judah. Two approaches of commentators diverge, however, depending on how literal the text reads.
Non-Literal
While these commentators concur Yeshayahu's action took place in public, they dilute the potency of "עָרוֹם וְיָחֵף" to accord the story with the standards we have for our prophets.
וּפִתַּחְתָּ הַשַּׂק מֵעַל מׇתְנֶיךָ וְנַעַלְךָ תַחֲלֹץ מֵעַל רַגְלֶךָ – RashiYeshayahu 20About R. Shelomo Yitzchaki and Targum Pseudo-Yonatan understand וּפִתַּחְתָּ to mean the putting on of the sackcloth.2 Most other commentators understand וּפִתַּחְתָּ to mean the removal of the sackcloth.
עָרוֹם וְיָחֵף
Most commentators, following Yoma 77Yoma 77a-bAbout the Bavli assert Yeshayahu wore noticeably ripped clothing, where perhaps more skin was shown to the public.3
According to Rashi, שָׁלֹשׁ שָׁנִים qualifies both Yeshayahu's action and the future event related to Egypt. These commentators would take less issue with Yeshayahu walking around for a full three years as he was not fully unclothed.
Rasag argues Yeshayahu took only three steps in his עָרוֹם וְיָחֵף state. These three steps signified three years until the events related to Egypt took place.
Standards for prophets? This approach successfully neutralize this issue by redefining עָרוֹם וְיָחֵף.
The ashamed nations relying on Egypt and Cush – R. Eliezer of BeaugencyYeshayahu 20About R. Eliezer of Beaugency claims these verses refer exclusively to Egyptians and Cushites ashamed and dismayed of their own kingdoms. This prophecy has nothing to do with Israelites and is completely directed at Egyptians. According to RashiYeshayahu 20About R. Shelomo Yitzchaki, verse 5 refers to other surrounding nations that relied on Egypt an Cush for help. The "dwellers of this island" of verse 6 refers to those living in Israel who relied on Egypt for help.4
Goal of the Prophecy
Literal
Yeshayahu carried out Hashem's command in public and exactly how the verses make it. This effectively transmitted the prophecy's message to the people of Yehudah.
וּפִתַּחְתָּ הַשַּׂק מֵעַל מׇתְנֶיךָ וְנַעַלְךָ תַחֲלֹץ מֵעַל רַגְלֶךָ – Hashem indeed asked Yeshayahu to untie and remove his sackcloth as well as removing his shoes. עָרוֹם וְיָחֵף therefore literally means unclothed and barefoot.
עָרוֹם וְיָחֵף – These commentators assert עָרוֹם וְיָחֵף means completely unclothed and barefoot.
Vargon asserts that Yeshayahu's actions indeed took place over a three year period to make the biggest impression he could on the nation. While he wasn't constantly, publicly unclothed for that amount of time, Yeshayahu most likely would go into the public square at certain points, presumably enough times to make an impression.6
According to Rid, this is but another example of how prophets are expected to suffer as part of their roles as Hashem's messengers. Prophets knowingly accept such this burden when they consent to become the nation's prophet.
Similarly, the Keli Paz argues that though such a stunt would be a degradation to prophet, the honor of Hashem is at stake regarding the behavior of the nation and thus Hashem's honor would override the prophet's honor
The ashamed nations relying on Egypt and Cush/the dwellers of this island – Abarbanel reasons these verses refer to the Judeans who had placed their trust in Egypt and expected Egypt and Cush to come save them from the hands of the Assyrians.