I've always heard that Bernstein wrote the lyrics for 'One hand, one heart'. This song was written for Candide, but cut, and the re-used, memorably, in WSS. If its mostly the same lyric, then Sondheim would have had nothing to do with it,
John LaTouche wrote the Candide lyric to Bernstein's original melody, which had only one note per bar: "One / hand, / one / heart..." Sondheim found this too ponderous and convinced the composer to give him some extra notes to work with: "Make of our / hand / one / hand..."
I've never heard that Bernstein drafted a lyric for his original one bar, one note melody, but I suppose it's possible.
