From "Sinful Tunes and Spirituals, Dena J. Epstein, p. 245-246: "The Reverend Lewis Lockwood had heard "Go Down, Moses" at Fortress Monroe on September 3, 1861. By Dec. 2 he had sent an extended text of the song to the secretary of the YMCA in New York, who in turn sent it to the New York Tribune with a letter describing its circumstances. We do not know how much the text was edited in transit but this version appears to have been the first publication of the complete text of a Negro spiritual. The historic document was republished in the National Anti-Slavery Standard under the heading: "The Contrabands' Freedom Hymn" (See notes by Masato in his posting, above).
Mr. Lockwood said he took the words verbatim from the dictation of Carl Hollosay and other contrabands. "It was said to have been sung for at least fifteen or twenty years in Virginia and Maryland, and perhaps in the slave states...."
Lockwood made no attempt to preserve the dialect, "nor did he have a modern editor's respect for the integrity of the text, for he supplied a substantially different version for the sheet music edition."

The last three verses from the 1872 version (reproduced, above) do not appear in the 1861 version published in the National Anti-Slavery Standard 22 (Dec. 21, 1861) nor the version provided to the New York Tribune.
In the chorus, there is a slight difference:
O go down, Moses
Away down to Egypt's land.
And tell King Pharoah
To let my people go.

There are other small differences. In "The Song of the Contrabands" the first verse reads:
The Lord by Moses to Pharoah said:
"O let my people go!
If not I'll smite your first born dead.
Then let my people go."