What does “God said” mean in Gen. 1:3,6,9,11,14,20,24,26? To ask what language God spoke during creation is absurd. God did not speak to a human before he created humans. What is the meaning of “God said” וַיֹּ֣אמֶר אֱלֹהִ֔ים during creation?
Eight times, God utters 'Let there be' or 'be there ...', expressing no more than a statement that something should exist. 'Be there light', and so on.
Genesis 1:3 (light), 1:6 (firmament/divide waters), 1:9 (waters gather/dry), 1:11 (earth bring forth), 1:14 (luminaries), 1:20 (creatures out of water), 1:24 (creatures out of earth), 1:26 (man).
(Notice that earth and waters existed already, verse 2, before God spoke in verse 3.)
God creates and none other can. God needs no permission. God requires no assistance.
Angelic powers ('principalities and powers' with precedence - arche) who are, themselves, created, may administer that creation thereafter, but they do not create it.
God therefore, during the creative process, communicates only because that communication is a part of the creative process.
And if the Creator - alone - creates and no other is involved, then that communication must, of necessity, be within Deity.
Further revelation indicates that this is, indeed, the case :
In the beginning was the Logos and the Logos was with God and God was the Logos, the same was in the beginning with Logos. [John 1:1,2 literal]
All things were made by him and without him was not anything made that was made. ...[John 1:3 KJV]
The communication was within Deity. Nothing was made in a haphazard, disorganised manner without definite purpose and without serious intent. There was intelligent communication, in word, regarding all that was done.
All that is made is an intelligent expression of the One who created.
All is expressive of Him who created all.
All reveals him who created all . . . .
.. the invisible things of him, from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead ... ... [Romans 1:20],
. . . for without Logos was nothing made that was made.
Without intelligent communication, within Deity, was nothing made that was made.
While Nigel did answer the question, this is how I would organize the answer:
The Hebrew language has many anthropomorphisms; in the language, but not necessarily in the concepts or theology. Here are some examples.
In the face of means in the presents of.
פָּנֶה … n.m. … face … 2. a. = presence, person, of י׳ Ex 33:14, 15, בְּפָנָיו … (BDB, 1977 p. 815-6)
Hand can be used for strength, power.
יָד … hand … 2. Fig. = strength, power … (BDB, 1977 p. 388)
Finger of God is used for act of God.
אֶצְבַּע …— 1. finger, … = act of God Ex 8:15 … (BDB, 1977 p. 840)
Closer to the expression “God said” in Gen. 1 is using by the mouth of for agency.
פֶּה … mouth … of agency, בְּפּ׳ by the mouth of 2 Ch 36:21, 22 … (BDB, 1977 p. 804-5)
In 2 Chron. 36:22 בְּפִ֣י יִרְמְיָ֑הוּ, “by mouth of Jeremiah” = “by Jeremiah” in the JPS translation.
While “God said” in Gen. 1 has the idea of agency, it expresses more. It basically expresses the same idea as Ἐν ἀρχῇ ἦν ὁ λόγος (John 1:1, NA28, “In the beginning was the Word,” ESV). For the Greek, logos had the idea of reason or reasoning.
Essential to our ability to think is language. We think in words. Images of brain activity have shown that thoughts activate the same areas of the brain as when we say the words we are thinking. This is one aspect of humans being created in the image of God. Of life on Earth only humans have language that includes both logical and written language as opposed to merely emotional expression. But what is this saying about God? God is not an impersonal set of scientific principles. That is a part of creation; not a part of God.
For as the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts. (Isa. 55:9, ESV)
While explaining God’s thoughts in terms of our thoughts is an insufficient explanation, God created the universe with a plan and purpose. God did more than set the universe in motion like winding up a clock and releasing it. He created the Earth in stages, and throughout the Bible continued to interact in history.