These two verses are closely related in meaning, with verse 20 expressing the purpose of knowing the locations mentioned in verse 19. In verse 19 light and darkness are regarded as persons who have dwellings. Each comes out from its dwelling and later returns to it. The light leaves its home in the morning and returns to it at night, then darkness comes from its dwelling to return at dawn. Where is the way to the dwelling of light…? can be translated easily if it is possible to retain the personification. For example, Bible en français courant says “Do you know where the light lives?” Good News Translation avoids the figurative expression: “Do you know where the light comes from?” The light refers to the kind of light made by the sun and is the same word used in Genesis 1.3.
And where is the place of darkness: place corresponds to dwelling in the previous line. This line recalls Job’s question in 28.12b “where is the place of understanding?” Bible en français courant pushes the irony of the personification further than the text may imply: “at what address can one find darkness?” Good News Translation “or what the source of darkness is?” is a suitable rendering. Die Bibel im heutigen Deutsch has “from what place does darkness come?” In some languages it may be possible to render verse 19 as “Do you know where to go to find the light or where to find darkness?” or “Do you know where the light goes or from where darkness comes?”
That you may take it to its territory: it in both lines is singular in Hebrew, but refers to the light and the darkness in verse 19. Therefore it is best to use the plural, as in Good News Translation “them.” The notion is that Job would have to know where light and darkness live in order to lead them out to their territory, that is, to the place where they do their work, “… so that you could show them the way to their place of work.”
And that you may discern the paths to its home: only by knowing the path to their dwellings could the light and darkness know where to go when they stop working. It is possible to express verses 19 and 20 as condition and consequence. For example, “If you know the path to the dwelling of the light and the place where darkness lives, then you may lead them out to their work and back to their homes.” In languages in which the figures of dwellings for light and darkness will be unclear, it may be possible to render verse 20 as “If you know, you should be able to show them where they are to go and where they are to return.”
Quoted with permission from Reyburn, Wiliam. A Handbook on Job. (UBS Helps for Translators). New York: UBS, 1992. For this and other handbooks for translators see here .