The Kiddush (sanctification prayer) for Shabat contains the text "zikaron leMa’aseh bereshit" and "zecher leYetziat mitzraim". The linking of Shabat with creation is obvious (G-d created the world in 6 days and rested on the 7th), but why the exodus?
The source for remembering the exodus on Shabat can be found in Devarim 5, 13-14:
13 but the seventh day is a sabbath unto the LORD thy God, in it thou shalt not do any manner of work, thou, nor thy son, nor thy daughter, nor thy man-servant, nor thy maid-servant, nor thine ox, nor thine ass, nor any of thy cattle, nor thy stranger that is within thy gates; that thy man-servant and thy maid-servant may rest as well as thou.
14 And thou shalt remember that thou was a servant in the land of Egypt, and the LORD thy God brought thee out thence by a mighty hand and by an outstretched arm; therefore the LORD thy God commanded thee to keep the sabbath day.
There are several explanations proposed for this puzzling commandment (see Rabbi Flug: Yetziat Mitzrayim and its role in Shabbat and Yom Tov):
- To remind us that we were once servants in Egypt, and that we should allow our servants to rest (Ibn Ezra, Devarim 5:14).
- To celebrate that G-d freed us from slavery (Maimonides, Guide for the Perplexed 2:31).
- Shabat reminds us that G-d is the creator, in the exodus He asserted his power over creation, serving to reinforce the message (Ramban, Devarim 5:14).
- Because Shabat is a model for all holidays and all holidays are connected to the exodus (Sefer Abudraham, Ma’ariv for Shabbat).