After we receive the Lord's Supper, we sing in response to this wonderful gift of God. Such singing is reflective of the song Moses and the Israelites compose and sing in Exodus 15 after they are saved from the Egyptians, crossing the Red Sea on dry ground. Such singing is reflective of the song Deborah and Barak sing in Judges 5 after they defeat Jabin and Sisera.
And such singing is reflective of one of the options for the post-communion canticle, the words of Simeon after he meets baby Jesus in the temple. Simeon says, and we often sing:
"Lord, now you are letting your servant depart in peace, according to your word; for my eyes have seen your salvation that you have prepared in the presence of all the peoples, a light for revelation to the Gentiles, and for glory to your people Israel" (Luke 2:29-32).
After Simeon sees Jesus, all is well. After we receive the Lord's Supper, all is well.
It is a moment of intense relief and joy. A burden (all our sin) is lifted from us that is so freeing, we feel like we can finally breathe again. It reminds me of that moment in The Lord of the Rings when the ring is finally destroyed, and Frodo says, "It's gone! It's done!"
Our songs in response to God's marvelous actions continue to echo Moses, Deborah, and Simeon.
As another version of the Post-Communion Canticle puts it:
"Thank the Lord and sing His praise; tell everyone what He has done."