"Remember... the strong hand and the outstretched arm with which the Lord your God brought you out of Egypt." (Deuteronomy 7:19)
We are familiar with this phrase from the Haggadah that we read every year on Passover. But what exactly do the "strong hand" and "outstretched arm" refer to?
Strong Hand - Dramatic Transformation
If the objective of the Exodus had been only to liberate the Israelites from slavery and raise them up to the level of the other free nations of the world, then no special Divine intervention would have been necessary. By the usual laws of nature and history, the Jewish people would have gradually progressed to a degree of culture and morality prevalent among nations.
However, God wanted the newly-freed slaves to swiftly attain a high moral and spiritual standing. In order to prepare them for their unique destiny, they needed God's "strong hand". This metaphor implies a forceful intervention, overcoming the natural forces of the universe. God's "strong hand" dramatically raised the Jewish people from the depths of defilement and degradation to the spiritual heights of Sinai. 
By virtue of our inner nature, we will slowly but surely realize our true potential.
This sudden elevation of the people, the "strong hand", is commemorated by the rapidly-baked matzah. This reason for eating matzah is given explicitly in the Haggadah: "Because there was not time for the dough of our fathers to leaven before the King over all kings, the Holy One, revealed Himself to them and redeemed them."
Outstretched Arm - Towards the Future
The "outstretched arm," on the other hand, implies an unrealized potential, a work in progress. The Hebrew word for "arm" is zero'a, from the root zera ("seed"), indicating future growth. Even today, the ultimate goal of the Exodus has still not been fully achieved. The process of perfecting and redeeming the Jewish people is one of gradual progression.
If matzah commemorates the sudden redemptive quality of God's "strong hand", then which Passover food symbolizes the "outstretched arm"? That would be the maror, the bitter herbs. The maror reminds us of the bitterness of slavery. The very fact that we felt this bitterness is an indication that servitude contradicts our true essence. By virtue of our inner nature, we will slowly but surely realize our true potential.
While the "strong hand" gave the initial push, it is through the "outstretched arm" that we steadily advance towards our final goal. This progress is accomplished through the mitzvot, which refine and elevate us. It is for this reason that all mitzvot are fundamentally connected to the redemption from Egypt.
[Adapted from Olat Re'iyah vol. II, pp. 279-283]