The song is Oh Freedom (see this wikipedia article for some lyrics: Oh Freedom).

The song seems to have been chiefly associated with Odetta (though Joan Baez certainly also sang it). I've looked through a Buffy discography up to the 90s and it doesn't seem to be listed there. That doesn't mean she didn't do it though.

(I also can't find any lyrics listed using home to my fathers rather than home to my Lord).

Mick