"
Long lay the world
In sin and error pining
It says this because the world was full of sin and error everywhere. Jesus was sent so that he could try to fix all the wrong. Ever since the beginning with Adam and Eve when they broke God's rules in the Garden of Eden and were led on by the snake (which represented the devil/temptation), the world was full of temptation and sin. When they were crucifying Jesus and he was dying, he called out to God and forgave everyone's sins for doing that to him.