The correct answer to this open question is the following.
I am going to pick one of the most famous spirituals from the Civil war era. This is a song called "Go Down Moses."
One of the lines says: "Oppressed so hard they could not stand
Let my people go!"
It is a beautiful song that was one of the favorites of black soldiers in the Union Army. It is like a form of prayer-song, where black people asked help to God. The meaning of the song is that God allows its people to be free from the oppressor.
Later, in the 1920s, Jazz singer Loui Amstrong sang the song and made it more popular in different audiences.
Other famous spirituals form the Civil War era were "Nobody Knows the Trouble I've Seen" and "Free at Last."