The real force of the story is unveiled in the second part of v 25: There the LORD made for them a statute and a rule, and there he tested them. The LORD was leading his people. He was the one who led them to Marah. The LORD was the one who, in their desperate need for water, brought them first to the bitter waters. But v 25 is the divine perspective on these earthly affairs. Marah was a test. The Lord was trying his people to see if they would trust him. Thus the lesson from God’s Word is, in times of great difficulty, we must trust the Lord.
What do you do when you realize that God has saved you? You sing. Brothers, God’s people sing. In Gen 4, we learn that Jubal made musical instruments. Job mentions singing a handful of times. But this is the first time that singing appears canonically in the Scriptures. How appropriate that, after such a monumental event displaying God’s covenant love, that it is here that we see his people joining in song. The central point from this text for us is simply this: Sing to the LORD. But when I say that this passage urges us to sing to the LORD, I am getting after something more fundamental than mere singing. Indeed, I want us to have the heart to sing to God. My concern is that there is in each of our hearts joyful affections in Christ our Savior.