Blood
Revelation tells us of a vision John had of the end of time. We get to see how history ends. At the end, Jesus receives praise for the sacrifice he made for us on the cross. In verse 5, we see one reason for praise is Him giving His blood for us. Later in chapter 5, Jesus is praised again as the Lamb who was slaughtered - a reference to the ceremonies we read about in Leviticus. Those lambs that were killed were a picture of Jesus who was to come and die for our sin.
When we read Psalm 136, you were encouraged to repeat a phrase about God’s love throughout your day. Perhaps today you could repeat the phrase, “Worthy is the Lamb who gave His life for me.”