Genèse 3:8

(8) And they heard- there are many medrashic agadot, and they have already been organized in Bereishit Raba and in other Medrashot. I have only come to (arrive at or help explain) pshuto shel mikra, the plain meaning of the text, and to (bring at times) the agadic works that settle the words of the Torah, each word in its place.

And they heard the voice of the Word of the Lord God walking in the garden in the repose of the day; and Adam and his wife hid themselves from before the Lord God among the trees of the garden.

AND THEY HEARD THE VOICE OF THE ETERNAL G-D WALKING IN THE GARDEN. The Rabbis have said in Bereshith Rabbah: “Rabbi Chilfi said that from here we may learn that a voice ‘walks,’ for it is said, And they heard the voice of the Eternal G-d walking.” And so did the Rabbi [Moshe ben Maimon] write in Moreh Nebuchim. that is modified by walking.” And so is the opinion of Rabbi Abraham ibn Ezra that “walking” refers to “the voice,” just as in the verse: The sound thereof shall go like the serpent’s. And Ibn Ezra further says that the meaning of toward the cool of the day is that they heard the voice towards evening. And he mentioned in the name of Rabbi Jonah ibn Ganach that the meaning of the verse is: “and man was walking in the garden toward the cool of the day,” [the sense of the verse thus being that while man was walking in the garden, he heard the voice of G-d].
In my opinion, the sense of walking in the garden of Eden is similar to that of the verses: And I will walk among you; And the Eternal went as soon as He had finished speaking with Abraham; I will go and return to My place. All these verses indicate a revelation of the Divine Presence in that place or the departure from the place wherein He was revealed. The sense of the expression, toward the cool of the day, is that with the revelation of the Divine Presence comes a great and strong wind, even as it says, And, behold, the Eternal passed by, and a great and strong wind rent the mountains, and broke in pieces the rocks before the Eternal. Similarly we find: Yea, He did swoop down upon the wings of the wind; and in the book of Job it is written, Then the Eternal answered Job out of the whirlwind. Therefore Scripture says here that they heard the voice of G-d as the Divine Presence was revealed in the garden approaching them in the wind of the day, because the breath of the Eternal blew upon it, that is, in the garden, like the wind of ordinary days, not a great and strong wind as in the vision of other prophecies, in order that they should not be frightened or terrified. Yet Scripture says that in spite of this they hid themselves on account of their nakedness. In Bereshith Rabbah we find that the Rabbis also said: “Said Rabbi Aba the son of Kahana: ‘Mehalech (walking) is not written here but mith’halech (meaning “it leaped and ascended).” Rabbi Aba thus interpreted the word mith’halech similarly to that of And the Eternal went, as we have explained the term “walking,” except that he explained the verse before us as referring to the withdrawal of the Divine Presence that dwelt in the garden of Eden and its retiring therefrom on account of the sin of Adam, even as it says, I will go and return to My place. We interpret it to mean the revelation of the Divine Presence in that place, which is the correct and fitting explanation of the verse.

וישמעו את קול ה' אלוקים מתהלך בגן לרוח היום, referring to the author’s commentary on Exodus 14,30, it appears that he understands the word מתהלך, as does Rabbi Chalfan in Bereshit Rabbah 19,7 where that Rabbi says that the word מתהלך modifies the word קול.

מתהלך בגן, back and forth, in accordance with the requirements of their purpose. The word is similar in meaning to Genesis 13,17 where Avraham is instructed by G’d התהלך to “crisscross the land of Canaan, in order to symbolically lay claim to it.” The same construction is also found in Psalms 105,13 ויתהלכו מגוי אל גוי, “they wandered from nation to nation.”

לרוח היום, according to His pleasure on that day. The word רוח is used in the abstract, spiritual sense, not referring to a breeze. This is no different that what G’d had also done during the other days of creation, and as He had been doing on this same day (sixth day of creation) prior to Adam’s sin.

ויתחבא, as the Torah wrote in Deuteronomy 23,15 ולא יראה בך ערות דבר, “no exposure of genitals (or other shameful matters) shall be visible on you.”

וישמעו, some commentators explain what happened not as G’d’s voice “walking,” but as Adam and Chavah walking and hearing the voice of G’d while going for a walk. If that were correct, the word “they heard” should have been written after our being informed that they had been walking in the garden. Besides, the word מתהלך should have been in the plural mode. The correct interpretation of the verse is: while Adam and Chavah went for a walk they heard the voice of G’d “going for a walk.” We have a precedent for this, i.e. the “voice” of the serpent being described as “walking” in Jeremiah 46,22.

לרוח היום, towards evening, when the day becomes cooler and the breeze blows. He recognized at once that the voice belonged to G’d, and that G’d had come to speak to them about their sin. As a result, they hid among the trees of the garden out of shame over the fact that their genitals were exposed. Even though they had made these חגורות for themselves by sewing together the fig leaves, these were not enough to hide the areas of their bodies they felt ashamed of. They were perfectly aware, of course, that it is impossible to “hide” from G’d, else their entire intelligence would not have amounted to much. The Torah merely describes that they reacted in the time honoured human fashion when one is ashamed and wishes to hide the source of one’s shame.
The reason why the Torah informs us that they heard G’d’s “voice” before they heard what He had to say, is that the Torah wishes to teach us something about good manners. 1) G’d wanted to give them an opportunity to hide; 2) one should not frighten people by addressing them suddenly without a person having had a chance to compose himself first in order to receive a visitor and to meet such a visitor after preparing for his visit. One should either knock on the door, or try and make voice contact by inquiring if the person is at home, etc. (Massechet Derech Eretz ) The reason why the Torah had to mention the expression רוח היום is that the wind carried the sound of the voice to them.

עץ הגן, the word עץ here does not refer to a specific tree, but to the category of “trees,” as opposed to other, smaller plants. They took refuge due to their feeling of shame.