I [G‑d] will pass through the land of Egypt on that night…." (Ex. 12:12)

The Jewish people had sunk almost to the nadir of impurity in Egypt, to the 49th of the fifty levels of impurity (Zohar Chadash, beginning of parashat Yitro), and had thus become almost fully absorbed into the mentality of Egyptian culture. The basis of Egyptian civilization was the belief in the supremacy and immutability of the laws of nature; therefore, in order to extricate the Jewish people from Egyptian materialism, G‑d could not just "send an emissary", i.e. any created being. He could not oppose the idolatry of nature with a force that was itself part of Creation and subject to its laws. He had to reveal the aspect of Himself that transcends creation and its natural laws.

…I Myself and none other." (Rashi on ibid.)

Good and evil are ultimately arbitrary concepts that G‑d created and defined for use in the created world….

Having already excluded all other emissaries, what does this expression serve to exclude? Whenever G‑d reveals that aspect of Himself that transcends Creation, He is also revealing that aspect of Himself that transcends the dichotomy of good and evil. After all, good and evil are ultimately arbitrary concepts that G‑d created and defined for use in the created world. Therefore, whenever this level of divinity is operative within Creation, evil can claim equal legitimacy along with good. Precautions must therefore be taken to ensure that this does not happen.

G‑d therefore closed His announcement of this imminent revelation with the promise that He will not allow forces that are not subordinate to His will to take advantage of it. In other words, His revelation of His transcendence will be accompanied by the revelation that despite the moral equivalency of good and evil at this level, He still prefers good over evil.

Adapted from Likutei Sichot, vol. 13, p. 855; Likutei Torah 2:12c-d
© 2001 Chabad of California/www.LAchumash.org