What is the theme in Swing Low Sweet Chariot ?

Religion is the main theme in the book. The figure of a god riding across the sky in a chariot goes back to Greek mythology, in which Apollo was said to ride the sun as a chariot over the earth during the daylight hours. It is an image of heaven's magnificence, combining the chariot, which symbolized the wealth and power enjoyed by a king, with the superhuman power of flight. The heavenly chariot can also represent trouble for mankind, as in ancient images of Zeus, king of the Greek gods, driving his chariot with one hand and hurling thunderbolts at the earth with the other. In this poem, the chariot is welcome; the speaker spec­ifies that it is coming to carry him or her "home."