The Torah states clearly that the Egyptian exodus took place in the evening. This is reiterated in pasuk 6, when the Torah says to slaughter the Korban Pesach after the sun descends, “the appointed time of your departure from Egypt.” If this is the case, why does the Torah in pasuk 3 declare that we should “remember the day of your departure from the land of Egypt“? There seems to be an apparent contradiction between the pesukim concerning exactly when Klal Yisrael left Egypt. The Talmud in Berachos 9A identifies the “shaas chipazon” of Klal Yisrael, which occurred the following day at midnight when the Egyptian firstborn died. After this occurrence, the Egyptians proceeded to the Jews and told them to leave. The Jews did not leave, however, until morning. From the Egyptian point of view, the Exodus took place at night, although the Jews did not actually leave until the next day. In other words, there were two yetzios, departures: one from Mitzrayim, Egypt, at night, and one from Eretz Mitzrayim, the land of Egypt , which took place by day.
Horav Shimon Schwab,zl, gives insight into these two departures and explains the corresponding text which seems to distinguish between Egypt and the land of Egypt. When Hashem commanded Klal Yisrael to slaughter the Korban Pesach, the lamb which served as the Egyptian godhead, to smear its blood on the doorpost and lintel, their homes became Batei Yisrael, Jewish homes – islands of spirituality and morality amidst a sea of pagan hedonism. They were instructed not to leave their homes that night. They had already departed from the Egyptian culture and lifestyle. They were no longer assimilated into Egyptian culture.
This metamorphosis took place while Klal Yisrael was still in the land of Egypt. Consequently, the Torah emphasizes that they had left Egypt while they were still in the land. They were not out of Egypt, but Egypt was no longer a part of them. During the next day, Klal Yisrael completed the Exodus — by actually leaving the land.