Harry's Blues Lyrics gives slightly different versions of some lines. I haven't heard the original Blind Willie version, so I offer these lines only for comparison.
verse 2 line 3- She said I would accomplish
verse 3 line 6- To bear my burdens away
verse 4 line 2- I'd pray for a little while

Eva Jessye arranged the spiritual fragments and was choral director for the original "Porgy and Bess" opera. The Jessye Choir can be heard on out-of-print albums of songs from "Porgy and Bess."

Unfortunately, there seem to be no recordings of other songs sung by this choir, which toured successfully years ago. Or maybe I just failed to find any.