“And the L-RD said unto Moses: ‘Wherefore criest thou unto Me? Speak unto the children of Israel, that they go forward.'” – Exodus 14:15, JPS 1917 Tanach
The seventh day of Pesach, Nissan 21 corresponds to the day on the Hebrew calendar when the Sea parted: The Children of Israel hesitated. Moshe cried out to G-d. H’Shem told him to “Speak to the Children of Israel, that they go forward.” Having already prayed for deliverance, the time was at hand; there was no further need for prayer, despite the imminent threat of the Egyptian army, poised opposite the encampment of B’nei Yisrael at the Sea of Reeds.
An east wind from H’Shem caused the sea to part, and dried the floor of the sea for the safe passage of the Children Israel. Of this miracle, Melchita notes, as commentary to the Children of Israels words in the song of Moshe, “this is my G-d, and I will exalt Him” (Exodus 15:2), that even the lowliest handmaid saw in terms of HShem’s revelation through the forces of nature, what the prophets, later in Jewish history did not see.
Additionally, the level of kedushah (holiness) that they received after crossing through the Sea, and the sublime experience at Sinai, when H’Shem revealed Himself to them, brought them to a level, where as a cleansed vessel, the Shechinah could dwell within them. The sea served as a mikveh (receptacle); and, tevillah (immersion) in the waters of the sea signified the beginning of a new start, a renewal of mind, body, and spirit; in essence, a rebirth, through purification in a mikveh, and the indwelling of the Shechinah, as mentioned in Exodus Rabbah 23:12.