"And he took six hundred chosen chariots"
Rabbi Yosi says that the 600 chosen chariots correspond to the number of the children of Yisrael, "about 600,000 men on foot." Rabbi Chiya tells us that when the Holy One, blessed be He, gives dominion to the ministers of the nations above, He gives it to their nations below, and when He brings them down from their grade above, He brings down their nations below. The minister of Egypt led the chariots of the other peoples, all of whom fell into the sea. Rabbi Chiya explains how Pharaoh harnessed the mares before the stallions, then the stallions before the mares, depending on whether he wanted them to run, or to fight. He compares this to the verse, "And Hashem went before them by day," saying that afterwards the Shechinah went behind the children of Yisrael.