This coming Saturday night, April 19, the holiday of Passover begins

and we celebrate the first Passover seder. Among the many customs and laws that surround the seder is the obligation to drink four cups of wine, to recall the four expressions of redemption written in the Torah.
When G-d told Moses that He would free the Jewish people from Egyptian enslavement, He used four different terms:
1. "V'hotzeiti - I will take you out,"
2. "V'hitzalti - I will save you,"
3. "V'ga'alti - I will redeem you,"
4. "V'lakachti - I will take you."
These four expressions correspond to the four decrees that Pharaoh issued against the Jews: the decree of hard labor, the decree that the midwives should kill all male children, the decree that all baby boys should be drowned in the Nile, and the decree to withhold from the Jews the straw necessary to make bricks, even though the quota of bricks to be filled wasn't decreased. For each additional act of cruelty, G-d promised to free His people.
However, if we continue reading the Torah, we come across yet a fifth expression of redemption, "V'heiveiti - I will bring," meaning that not only will G-d take the Jews out of their misery, but He will continue to take them out until they have reached the land that He has promised to them. This is considered the last term of redemption, the one that will be fulfilled with the coming of Moshiach. This fifth term is also symbolized by a cup of wine at the seder, Elijah's cup.
The Rebbe notes that the custom of Elijah's cup is not mentioned in the Talmud or in any of the earlier texts regarding Jewish law. Its earliest source is in the writings of the sixteenth century. This is attributed to the fact that pouring a cup for Elijah is an expression of our faith in the coming of Moshiach, and with each passing year the feeling of anticipation grows stronger and more widespread.
This year, may we see the fulfillment of our anticipation as we conclude the seder with the words, "Next year in Jerusalem," when G-d will fulfill His fifth and final promise with the revelation of Moshiach and the Redemption.