וַיַּ֤רְא רֵאשִׁית֙ ל֔וֹ כִּי־שָׁ֛ם חֶלְקַ֥ת מְחֹקֵ֖ק סָפ֑וּן וַיֵּתֵא֙ רָ֣אשֵׁי עָ֔ם צִדְקַ֤ת יְהוָה֙ עָשָׂ֔ה וּמִשְׁפָּטָ֖יו עִם־יִשְׂרָאֵֽל׃ (ס)
און ער האָט אױסגעקוקט דאָס ערשטע פֿאַר זיך, װײַל דאָרט איז דער חלק פֿאַר אַ הערשער באַהאַלטן. אָבער ער איז געקומען פֿאַרױס פֿאַרן פֿאָלק; די גערעכטיקײט פֿון גאָט האָט ער געטאָן, און זײַנע משפּטים, אין אײנעם מיט ישׂראל.
Ibn Ezra
Our sages have said that the [letter] bet was added, like the bet in barishonah (“in the beginning”) Bereshit 13:4, for you find “at the beginning (rishonah) they travelled” Bamidbar 2:9. But were that the meaning, the bet would have been vocalized with a kamatz gadol. And there are those who say that [the word] bereshit always [appears in] attached [form], where the meaning is “at the beginning of the evening, or the night, or the darkness”. But behold, they forgot “he saw a beginning reishit for himself” Devarim 33:21. And there are those who say that the bet is a subject without meaning. Their reason is that it is unthinkable that there is no beginning to the heavens and the earth. Therefore, it said “bereshit. But according to my opinion, it is indeed an attached form, like “At the beginning (bereshit) of the rule of Yehoyakim” Yirmiyahu 26:1. Now don’t wonder how can it be attached to a past tense verb [instead of a noun], for behold, thus: “At the beginning (techilat) spoke Hashem with Hoshea, and Hashem said to Hoshea” Hoshea 1:2, “The city (kiryat) where David camped” Yishayahu 29:1. The meaning [of this usage] will be explained for you in the second verse.
Radak
בראשית ברא אלוקים את השמים ואת הארץ. The word Bereshit is not in a genitive possessive mode, i.e. “at the beginning of,” as for instance in Jeremiah 26,1 where we find בראשית ממלכת יהויקים, where it means: “at the beginning of the reign of Yehoyakim,” but is a word in its own right as in Isaiah 46,10 מגיד מראשית אחרית, “foretelling the end from the beginning,” or, as in Deuteronomy 33,21 וירא ראשית לו, “He chose the choicest for himself.” In other words: when G’d began to create the universe, He first created heaven and earth. The word בראשית is necessary as one cannot speak of either ראשית or אחרית except in terms of “time.” At that point “time” did not exist yet as it is a concept indivisibly linked to motion. Motion commenced only when the planets were placed in the sky (on the fourth day). These motions were described in terms of “days.” At the “time” described in our verse there were only “moments,” “hours,” etc., but a recurring cycle of time such as days had not yet come into existence.
Chizkuni
בראשית; Rashi comments on this word as follows: “Rabbi Yitzchok said that there was not really any need to commence the Torah before the beginning of chapter 12 in Exodus, when G-d addressed the Jewish nation with legislation about the forthcoming Passover. He only did so in order to tell mankind that He owns the earth and therefore can allocate parts of it to those, whom He chooses, i.e. that the Israelites did not rob the Canaanites of their land, which had never been rightfully theirs. Rashi therefore considers the laws about Passover as the first commandment given to the Jewish people. If we were to counter that the seven universal laws that apply to all of mankind apply to us also, and these had been given many years before there was an Avraham, even, the answer is that what Rashi meant was the Passover legislation was the first commandment given to the Jewish people when all of them were present during that address. (Exodus 12,3) To the question that the mere idea of the Canaanites arguing that the Israelites had stolen their land, seeing that what belongs to the slave automatically belongs to his master, and Canaan (Noach’s grandson) had been demoted to being a slave by his grandfather ever since he had been cursed, so how could they have ever owned it? (compare Genesis 9,26) Canaan’s descendants had been slaves of Shem, the great-grandfather of Avraham ever since! Rashi himself pointed this out already on Genesis 12,6. The Canaanites, as alluded to in that verse, had robbed the descendants of Shem of their heritage! We would have to answer that the Canaanites i.e. the tribes making up that kingdom, also contained kings (King of Chatzor) and others who were not descended from the original Canaan. (Compare Joshua, beginning chapter 11) The latter might even have been descended from Shem, so that the Israelites would have had a legal claim on the land they occupied as they were rightful owners. An alternate way of explaining why the Torah commenced with the word (and the story that follows) of בראשית is this. It is to inform us of the sequence in which this material universe came into existence and how once created it was allocated to the creatures inhabiting it, as Rashi explained, i.e. to prove that the Canaanites had no legal claim to dispute the Jews’ viewing it as their inheritance, ancestral heritage, by claiming that rightfully Eylam had a legal claim to it. [Eylam was Shem’s firstborn son, (Genesis 10,21, whereas Avraham was a descendant of Shem’s youngest son Arpachshad, basing themselves on what is written in Genesis 11,13 where this son is listed last, not first as in 10,21. Ed.] Yet another reason for the Torah commencing with the words: בראשית ברא אלוקים, “at the beginning G-d created, etc.;” is to state categorically that the universe in which we live did not exist eternally, or is the result of “the big bang,” but was created by a Creator. When Rashi states that G-d allocated the land of Israel to the Israelites מרצונו, “as an expression of His goodwill,” this is an implied warning that such an allocation was not absolute and irreversible for all future time, otherwise how could He take it back by exiling its people and reallocate it to someone else? Rashi also makes the point that the word ראשית, whenever it occurs in the Bible is invariably linked to the word following it. The author, supporting Rashi, cites an example from Leviticus 2,12: קרבן ראשית תקריבו אותם, “you are to present them as an initial offering.” [Rabbi Chavell, in his annotations, already pointed out that the author’s statement is not quite accurate, pointing to Deuteronomy 33,21, וירא ראשית לו. Ed.]