I'm not sure you can pull this one off with just 3 chords, but it ain't all that bad, really.
According to the Hymnal (I really like Hymnals that give you the chords) "Fruits Of Worship" #245 they go (Key of "G"):
G - C - G - D7 - G - Am - G - D7-G - (C) - D7 - G - Am - C-G - D7-G.
You probably won't take long figuring out where they go in the song, and these chords work pretty well for me. I use a melodic fingerpicking style on the guitar; it would be nice on or with a mandolin, fiddle, bull-fiddle, or flute. I can't see a banjo adding much to this one, but some really clever ol' Picker just might get it to work.
It's got a few real pretty but tricky transitions in there, so listen to the MIDI on CyberHymnal (or a recording if you've got one) carefully several times over if you don't sight-read music real well (like I don't) so as to get the tune down solid. If you can get a Lady who can sing a nice soprano or alto harmony over your baritone or tenor melody, man; this one'll really give ye the collywobbles & goosebumps!
In the book they claim that the "Words" to Vs. 1,2,&4 are "Anonymous" and V.3 ("When tyrants tremble...") is attributed to Doris Plenn, (C) 1957, Sanga Music Inc.. Music: "American gospel hymn".