I'd like to elaborate a little on Dottard's good answer
Questions of Instantaneous and completeness of works
Genesis is ambiguous. In Gen 1.1, "God created the heavens and the earth". If that was completed, then why did God create light in verse 3? And why was the earth "without form" and void? That doesn't appear like a completed work.
Some say that between Gen 1.1 and Gen 1.2, a number of events happened, for example Satan fell, there was war, and the end of that age was a formless and chaotic earth that had to be rebuilt. The issue isn't whether this is true or not, but that this is a common interpretation in rabbinical traditions suggests that the language of Genesis allows this reading. Maybe it was completed in 1.1 or maybe the subsequent versus contain the completion of the work outlined in 1.1 -- both interpretations are reasonable.
As another point, a pattern in Genesis is
- God says
- God does (or someone does)
- God names (often translated as "calls")
For example:
- (v 3) "Let there be light"
- (v 4) "God divided the light from the darkness"
- (v 5) "God named the light 'Day'"
A lot of people put emphasis on the "yehi", which means "and it was". But you have the yehis all over:
God said, "Yehi light"
Light yehi.
[...]
And God named the light day and the darkness he named light.
yehi evening
yehi morning
Evening and Morning only get an "it was so" after they are named. Each yehi is a completion in some sense.
Now what's strange is how could God see the light if it was still mixed in with darkness and not yet divided from it? Well, let's say in God's eyes he could see it - God can see the light mixed in with darkness - but man could not yet see it.
But then in what sense is the work of creation of light "completed" in verse 3? In God's sense, it's completed. But then perhaps not in man's sense.
But now we get to verse 14:
"And God said,
[Let there be] lights in the firmament of the heaven to divide the day from the night;
and [let them be] for signs, and for seasons, and for days, and years:"
The "let there/them be" is the same yehi as "Let there be light".
So grammatically, there is no distinction between "let there be" in verse 1, except the word for "lights" is meoroth -- light sources. Like lamps. As opposed to light as a category.
So did God create the category in verse 3 and the actual lamps that provide a source of light in verse 14? Or did God create the lamps in verse 3 and they were only seen on earth in verse 14? Or did God create everything in verse 1, and God wanted to rekindle the light in verse 3 and then make it visible on earth in verse 14?
Moreover it is only in verse 14 that we see that darkness is divided from light. Was darkness divided from light as a category in verse 4, and then realized in verse 14, or was the work of dividing light from darkness only completed in verse 14? Or is God still dividing light from darkness even now, just in different places?
For example, say this separation in day 4 refers to the atmosphere clearing up so that the sun and stars could be seen, and this clearing up of the atmosphere is as a result of oxygen produced by green vegetation in day 3 -- then this would be an example of the separation that was declared among categories in verse 3 being realized on earth in verse 14.
It is with an appreciation of this ambiguity that we have to be careful when saying "in which verse did something happen?", as this is observer dependent, and so we need to pay attention whether the observer is God or creation generally, or man. Was the light seen by God, or in the universe, or on earth, or even in us? These are different notions of completeness for when God says "Let there be light".