The Torah says, “The Children of Israel went out b’yad ramah, with a high hand” (Ex. 14:8). Pinhas Peli points out that “The true Exodus actually came when the Israelites were ready to go out of Egypt with a ‘high hand'”.
Some versions understand this phrase as meaning “boldly”. The M’chilta explains it as “with uncovered heads”, which Shmuel David Luzzatto, the Shadal, believes denotes “with heads held high”, without fear or submissiveness. Rashi says it means, “In high-spirited and open bravery”.
As soon as the people were psychologically and spiritually ready to move into a new era, that was already the beginning of their exodus. Until then they were a slave people, overcome with “hard work and weariness of spirit” (Ex. 1).
Life was black – shachor. Once the Israelites were ready for redemption, shachor became shachar, the dawn.