This is an addendum to this post. I had asked:
Why was it necessary for B'nei Yisrael to eat the korban pesach fully dressed for their journey and with, חִפָּזוֹן, great speed?
And I answered:
It was in order to demonstrate their absolute conviction that Hashem would immediately redeem them (see Seforno). Additionally, this conviction in the immediacy of the geula was a further blow to the illusion of the power of Mitzrayim (i.e. they could leave immediately because no bureaucratic process would be necessary to slow them down).
However, it seems that even though B'nei Yisrael were commanded to eat the korban pesach fully dressed for their journey and with, חִפָּזוֹן, great speed they did not actually think that they would be leaving that morning. The Mitzrim forced them out (Sh'mot 12:33):
לג וַתֶּֽחֱזַ֤ק מִצְרַ֨יִם֙ עַל־הָעָ֔ם לְמַהֵ֖ר לְשַׁלְּחָ֣ם מִן־הָאָ֑רֶץ כִּ֥י אָֽמְר֖וּ כֻּלָּ֥נוּ מֵתִֽים׃
The Torah leaves little doubt in our minds about the reason for their harried exit, only six verses later it is written (12:39):
לט וַיֹּאפ֨וּ אֶת־הַבָּצֵ֜ק אֲשֶׁ֨ר הוֹצִ֧יאוּ מִמִּצְרַ֛יִם עֻגֹ֥ת מַצּ֖וֹת כִּ֣י לֹ֣א חָמֵ֑ץ כִּֽי־גֹרְשׁ֣וּ מִמִּצְרַ֗יִם וְלֹ֤א יָֽכְלוּ֙ לְהִתְמַהְמֵ֔הַּ וְגַם־צֵדָ֖ה לֹֽא־עָשׂ֥וּ לָהֶֽם׃
The very reason they made matza was because the Mitzrim forced them out. So for what reason did B'nei Yisrael think they were eating all dressed up for a journey? Even if they knew that they would be leaving in the morning - why would they get dressed for the journey in the middle of the night?
DL suggested the following: the way people dress reflects their frame of mind. They had to demonstrate while eating the Pesach their complete rejection of Mitzri society. By wearing their travel clothes they were showing that "in their minds they were already gone". In fact it would have been inappropriate for them to wear their house/lounging clothing which reflects a mindset of being settled in one's place. I give the following as an example: imagine quitting your job while still sitting comfortably at your desk. Would your boss take you seriously? I believe your boss's reaction would be quite different if you were to pack up all your stuff, put on your jacket, go to your bosses office and then tell him you quit. In the same way, B'nei Yisrael were demonstrating their quitting of Mitzrayim.