The conjunction For is a loose causal conjunction and should not link the first clause of verse 4 immediately with the final statement in verse 3.

Somewhere: in the Scriptures is implied. See discussion on 4.3. Somewhere is a vague reference, like that in 2.6, to Genesis 2.2. The expression somewhere in the Scriptures this is said may be rendered as “somewhere in the holy writings one may read.”

It may be necessary to specify that the seventh day refers to “the seventh day of the week” or “the seventh day of making the universe,” for it is not merely any seventh day.

In a number of languages temporal expressions may need to occur first in the sentence, especially if the temporal setting is emphasized. It may therefore be wise to restructure the direct quotation as “On the seventh day God rested from all that he had done” or, to make the activity more explicit, “… what he had done in creating the world.”

Quoted with permission from Ellingworth, Paul and Nida, Eugene A. A Handbook on The Letter of the Hebrews. (UBS Handbook Series). New York: UBS, 1983. For this and other handbooks for translators see here .