The Meaning of “Endless” in the Original Hebrew and Greek

Harvard professor Moses Stuart, writing in 1830:

The result seems to be plain, and philologically and exegetically certain.
It is this;

either the declarations of the Scriptures do not establish the facts, that God and his glory and praise and happiness are endless; nor that the happiness of the righteous in a future world, is endless; or else they establish the fact, that the punishment of the wicked is endless.

The whole stand or fall together.
There can, in the very nature of antithesis, be no room for rational doubt here, in what manner we should interpret the declarations of the sacred writers.
We must either admit the endless misery of hell, or give up the endless happiness of heaven.

—Moses Stuart, Exegetical Essays on Several Words Relating to Future Punishment (Philadelphia: Presbyterian Publication Committee, 1867 [reprint of 1830 edition]), 62; emphasis original.
HT: Robert Yarbrough