For the horses of Pharaoh with his chariots and his horsemen went into the sea, and the LORD brought back the waters of the sea on them; but the sons of Israel walked on dry land through the midst of the sea.  And Miriam the prophetess, Aaron’s sister, took the timbrel in her hand, and all the women went out after her with timbrels and with dancing.  And Miriam answered them, “Sing to the LORD, for He is highly exalted; the horse and his rider He has thrown into the sea.“

     Then Moses led Israel from the Red Sea, and they went out into the wilderness of Shur; and they went three days in the wilderness and found no water.  And when they came to Marah, they could not drink the waters of Marah, for they were bitter; therefore it was named Marah.  (Notice that immediately after being delivered from their slavery in Egypt and baptized into Moses in the cloud and in the sea–cf. 1 Cor 10:2–the people could find no water to drink except the bitter waters of Marah.  For this episode foreshadowed their coming to Sinai where Moses would receive the bitter spiritual waters of the law which like the waters of Marah the people could not drink.  In the very same way after being delivered from our slavery to sin and being baptized into the death of Christ, who lay three days in the grave, we are confronted with the bitter waters of the law–we want to serve and obey God, but how can we ever obey His righteous law and be holy as He is holy?)  So the people grumbled at Moses, saying, “What shall we drink?”  Then he cried out to the LORD, and the LORD showed him a tree; and he threw it into the waters, and the waters became sweet.  (That tree is the cross of Christ, for only the cross of Christ can make the bitter waters of the law sweet.  For only when we are crucified with Christ so as to die to the old man of sin can we be raised up with Christ in the power of His resurrection to live a life free from the control of sin and so fulfill the righteous requirements of the law, cf. Rom 6-8, esp. Rom 8:4.  Without the cross all of the law of commandments and statutes and regulations is bitter, for it can only arouse our sinful flesh so we bear fruit for death.  But by the cross we are made to die to that by which we were bound so that we serve in the newness of the Spirit and not in the oldness of the letter.  In this way the bitter water of the law is made sweet; indeed, with the cross “God’s commandments are not burdensome”, 1 Jn 5:3.)  There He made for them a statute and regulation, and there He tested them.  And He said, “If you will give earnest heed to the voice of the LORD your God, and do what is right in His sight, and give ear to His commandments, and keep all His statutes, I will put none of the diseases on you which I have put on the Egyptians; for I, the LORD, am your healer.”  Then they came to Elim where there were twelve springs of water and seventy date palms, and they camped there beside the waters.  (After we find the cross and are crucified with Christ so as to be raised up with Him and it is no longer ourselves who live but Christ who lives in us, then we are able to obey the righteous requirements of the law and experience the blessings spoken of here.  In the cross there is healing, and rest and peace and abundant provision; in the cross there are those twelve springs of the living water of the apostles of Christ by which we may abide to experience all the grace of God.)
Exodus 15:19-27