The
verse says:
כִּימֵי צֵאתְךָ, מֵאֶרֶץ מִצְרָיִם, אַרְאֶנּוּ, נִפְלָאוֹת
'As in the days of thy coming forth out of the land of Egypt will I show unto him marvellous things.'
What is going on behind the scenes that Hashem will allow miracles to occur during the Final Redemption like what occurred during the days of Egypt, but not earlier?
The
Sulam on Bereishit 53b explains that it's all due to sorcery. If it weren't for sorcery, the righteous would have the ability to perform miracles from the upper worlds in order to bring everyone closer to Hashem, similar to what happened during the Exodus and the later prophets. However, due to Adam's sin, the 4 worlds of אבי"ע were created on the other side - exactly corresponding to the 4 worlds of אבי"ע on the holy side - in order to distance people from Hashem, as it says
in Kohelet גַּם אֶת-זֶה לְעֻמַּת-זֶה, עָשָׂה הָאֱלֹהִים [God hath made even the one as well as the other]. Sorcery has an equal power to the holy side of the righteous to make miracles occur and veto miracles that come from the side of holiness. Therefore, only on very rare occasions does Hashem overrule the veto and allow for a miracle on the side of good to go through that brings the multitude of people closer and not be vetoed by the sorcerers - like during the Exodus and the time of the prophets.
When Mashiah comes, however, אראנו נפלאות - Hashem will show us miracles - just like when we were in Egypt because at that time, the power of Tum'ah will be nullified from the earth, and there will no longer be fear of the worlds of אבי"ע on the other side. Therefore, the righteous will be able to create miracles and wonders just like in Egypt.