The Paul and Silas verses used by Hamer are known in several forms in older spirituals. Here is part of a spiritual sung by Rebecca Taylor for Carl Sandburg and included in his 1927 "American Songbag:

ALL NIGHT LONG
1
Paul and Silas, bound in jail,
All night long.
One for to sing an' de other foh to pray,
All night long.
One for to sing an' de othah foh to pray,
All night long.
Do, Lawd, delibah po' me!
(two more verses; pp. 448-449, with musical score.)

The Stanley Bros. sang "Paul and Silas;" the first verse:
Paul and Silas bound in jail all night long, (3x)
Saying who shall deliver for me.

Hamer combined the Paul and Silas lines with lines from "Go down, Moses;" 'Let my people go,' etc. is from old spirituals.

I think search will show Hamer's lines and verses mostly are floaters used in several spirituals. The 'combination' might be new, but little else.