Genèse 1:3

And the Lord said, Let there be light and to enlighten above; and at once there was light.

“And He said” – The Gaon said that the meaning of vayomer (“And He said”) is like “and He desired”. But if this was so, it would have been appropriate for there to have been light [from the beginning, without darkness]. Rather, it’s in accordance with its [plain] meaning. And thus, “By the word of G-d were the heavens made” Psalms 33:6, “for He commanded and they were created” Psalms 148:5, The meaning is: a way of referring to an effortless action, comparable to a king and his servants. Now this light was above the wind.

AND G-D SAID, ‘LET THERE BE LIGHT.’ The word “saying” here indicates Will, as in the verse, What dost thy soul say, that I should do it for thee? which means, “What do you want and desire?” Similarly, And let her be thy master’s son’s wife, as the Eternal hath spoken means, “…as He hath willed, for such is the Will before Him.” Or, it may be [that the word “saying” here means] “thinking,” as in the verses, Thou sayest in thy heart; And the chiefs of Judah shall say in their heart. The purport is to state that the creation was not done with toil. Our Rabbis have also called this “thought.” Thus they have said: “The thought [concerning what was to be created on a particular day] was during the day; the deed itself was at sunset.” This teaches that creation was thought out, that there is a reason for everything created, that creation was not a simple manifestation of mere Will alone.
The word “being” [Let there ‘be’] indicates a deed for the present time,, since that light did not remain forever in its original state. just as: And thou wouldst be their king [meaning: their king from this moment on]. Therefore Scripture says that when He created the substance of the heavens, He said that from that substance there should come forth a shining matter called “light.”

AND THERE WAS LIGHT. The verse does not say, “And it was so,” as it is said on other days, because the light did not remain in this state all the time, as did the other creations. Concerning this matter, our Rabbis have an interpretation with a profound secret.
Know that the term “day” as used in the story of the creation was, in the case of the creation of heaven and earth, a real day, composed of hours and seconds, and there were six days like the six days of the workweek, as is the plain meaning of the verse. In the profounder sense, the Emanations issuing from the Most High are called “days,” for every Divine Saying, found in the chapter of Creation. which evoked an existence is called “day.” These were six, for Unto G-d there is the greatness, and the power, etc. The Sayings,, found in the chapter of Creation. however, are ten because regarding the first three Emanations, the term “day” does not apply at all. The explanation of the order of the verses in terms of this profound interpretation is sublime and recondite. Our knowledge of it is less than that of a drop from the vast ocean.

ויאמר אלוקים יהי אור, by means of this directive G’d meant to correct the fact that up until then everything was in complete darkness,

"Let there be light" - this is the light of the seven days [i.e., Or HaGanuz], which was for the use of those created without seed, and it will be [again] in the future, as the words of the Sages (may their memories be a blessing) Shabbat 30b: it will then be for that which is the future will "bring forth baked treats and fine clothing" without [needing] the power of seed.

ויאמר אלוקים יהי אור ויהי אור. The light was already in the heaven, seeing that the luminaries were created together with the planets. Daniel 12,3 refers to this when he compares the radiance of the knowledgeable people in the future to the radiance of the expanse of the sky, describing the latter as זהר הרקיע. In Exodus 24,10 the visions experienced by the elite of the Israelites is compared to וכעצם השמים לטוהר, “as pure as the radiant light of the heavens.” What had been lacking was only that this light had not illuminated the face of the deep as this had not been equipped to reflect such light as yet. Seeing that the directive concerned only the creatures in the “lower universe,” G’d did not introduce His creative activities with the words: יהי שמים, “let there be a heaven,” but the Torah wrote simply: “He created heaven, etc., ברא.” Once the various planets were placed in orbit to perform their orbits [I suppose that the sun only is meant, Ed.] every 12 hours the “lower” part of the universe would be in darkness. At the end of the first period of 12 hours, G’d issued the directive: “let there be light”, i.e that light should replace the darkness in that location. When the wind blows over the water it dries some of the surface of the waters enabling the waters to be illuminated faintly by the daylight above. The primordial light had not become distinct, strong, until the fourth day.
Possibly, the words זהר הרקיע describe the light by means of which the heaven itself shines, radiates light, as we have written. In that event, the light described here refers to a different period of 12 hours, a whole day comprising 24 hours. This light would have become missing on the first day from the “lower regions” of the universe. With the absence of this light darkness would have ensued in that region. During the first three days of the creative period, the only reason for such absence of light from part of the universe would be the fact that it was the will of the Creator that it be so. This can be so only if we adopt the view that the light prevailing during the first three days of that period was none other than the “natural” light radiated by the רקיע, the firmament. If, on the other hand, we assume that the light under discussion is the light of the sun, which up until then had shone weakly, seeing that the atmosphere had not been conditioned to let its rays traverse it without hindrance, and that as a result of this during these three “days” total …

יהי אור,ויהי אור, “let there be light, and there was light.” We are entitled to ask why the Torah wrote “there was light,” instead of writing that in response to G–d’s directive, ויהי כן, “and so it came to be,” instead of repeating the word: אור, “light.” The answer is that when referring to subsequent directives of G–d the Torah wished to be brief, and simply recorded that G–ds directive was carried out, here it could be spelled out in detail, as the word אור, being only one syllable, does not lengthen the report.