The NWT renders Gen 2:3: "And God proceeded to bless the seventh day and make it sacred, because on it he has been resting from all his work that God has created for the purpose of making."
The Hebrew SHAVATH is perfect state. Now the NWT elsewhere consistently renders Hebrew perfects as indicative of complete action and imperfect states as significative of ongoing or continuous action. For example, Gen 2:2 in the NWT reads:
"and he [God] proceeded to rest on the seventh day from all the work that he had made."
Now, if you study the footnotes for Gen 2:2-3 and the
appendix for the imperfect and perfect states in the
NWT, I believe it will help you to see why Gen 2:3 is
rendered "he has been resting."
Brenton's LXX has hOTI EN AUTHN KATEPAUSEN APO PANTWN TWN ERGWN AUTOU. KATEPAUSEN is aor ind act 3rd sg. This is interesting since the aorist tense generally delineates action as a whole:
"Since the aorist tense simply denotes occurrence without reference to initiation, progress, completion, or any such thing, it is usually translated from the indicative mood into English by a past tense" (Greek Enchiridion, W.G. MacDonald, page 9).
This is also what the qal perfect highlights (i.e.,
undefined action). The same morphological form,
KATEPAUSEN, appears in Heb 4:4. Therefore, it is
possible that Gen 2:3 may simply describe an action in
its entirety, leaving its temporal reference somewhat
As regards the qal stem, it is normally divided into
two classes: "verbs that represent action (fientive)
and verbs that describe a state of being (stative)"
(The Complete Word Study: Old Testament, page 2282).
Some sources that I have consulted say that there is
no "passive counterpart" to the qal stem; others
debate this point. At any rate, the qal perfect in Gen
2:3 seems to describe "simple, perfective action
viewed as a whole" (ibid., 2283).