How does Henry Garnet use religion as part of his argument against slavery?

Read the following quote from Frederick Douglass:

“Verily, the work does not end with the abolition of slavery, but only begins.”

What does Douglass mean by this statement?  What work might need to be done in 1865?

Explanation:

no statements but ok.

the statement that best describes the idea of manifest destiny that was used in the 19th century would be that "it was fate that the united states would continue to  expand westward," since people thought the us was "destined" to do so.