Ramban on Genesis 1:1
In the beginning, God created: Rabbi Yitshak said: "The Torah should not have been begun except from 'This month is for you,' (Exodus 12:2) which is the first commandment that Israel was commanded. And what is the reason that it opened with 'In the beginning?' So that if the nations of the world would say: 'you are thieves, since you conquered for yourselves the lands of the seven nations,' they would respond to them, 'all the earth is the Holy One's, blessed be He and He gave it to whomever it was fit in his eyes; and by His will He gave it to them and by His will, He took it from them and gave it to us.'"
And this is a tale in the words that our Rabbi Shlomo (Rashi) wrote in his commentaries. And one can question it, because there is great need to begin the Torah with "In the beginning God created" for it is the root of faith; and one who doesn't believe this and believes that the world is primordial is an apostate and has no Torah whatsoever.
And the answer, it is because the work of creation - it is a deep secret - is not intelligible from the verses, and will not be understood by its students except through the received tradition up until Moses our Master from the mouth of God [lit. "The Strength"], and those who know it are required to hide it. Therefore Rabbi Isaac said that beginning of the Torah doesn't require "In the beginning God created" and the story of what was created on the first day, and what was done on the second day and the remaining days, and the lengthy telling of the creation of Adam and Eve, and their sin and punishment, and the story of the Garden of Eden and Adam's exile from it, for all this cannot be understood with full understanding from the texts. And all the more so the story of the generation of the Deluge and the Division, for there is not great need of them.
And it would be sufficient for the people of the Torah without these texts, and they would believe in the general information that was mentioned to them in the Ten Commandments (Exodus 20:10): "For in six days God created the heavens and the earth, the sea and all they contain, and He rested on the seventh day", and the knowledge would remain to the few individuals among them, as 'a law given to Moses from Sinai" (halacha leMoshe miSinai), along with the Oral Law. And Rabbi Isaac gave a reason for this, that the Torah began with "In the beginning God created" and the story of the whole topic of creation until the creation of Adam, and that He made him ruler over the work of His hands and all that was given over beneath his feet, and the Garden of Eden - which is the best of all the places created in this world - became established for his dwelling, until his sin drove him from there.
And the people of the generation of the Deluge, by their sin were driven from the entire world, and the righteous one among them alone was spared, him and his sons. And their descendants, their sin caused them to be scattered in places and planted in lands, and they captured for themselves the places according to their families among their peoples, as the opportunities arose to them. If so, it is appropriate that when a people continues to sin, it will be destroyed from its place and another people will inherit his land, for this is the law of God in the world from always. And all the more so with what is told in the text that Canaan is cursed and was sold as an eternal slave, and it is not appropriate that he inherits the choicest places of settlement, but it will be inherited by the slaves of God, the seed of he who loved Him, like the matter which is written (Psalms 105:44), "And He gave them the lands of nations and the labor of peoples they shall inherit so that they shall keep His laws and guard His instructions."
That is to say, He chased out those who rebelled against Him, and settled in His servants, so that they would know that by serving Him they possess it - and if they sin against Him, the land will vomit them up as it vomited up the nation before them. And in order to elucidate the commentary that I have written [above, here] is the [Sages'] language in Bereishit Rabbah 1:3who stated it in the following language: "Rabbi Yehoshua of Sakhnin opened in the name of Rabbi Levi, '"The strength of his actions He told His people" (Psalms 111:6); what is the reason that the Holy One, blessed be He, revealed to Israel, what He created on the first day and what He created on the second day? Because of the seven [Canaanite] nations, so that they should not designate Israel and say to them, "Are you not a nation of looting?" and Israel will respond to them, "And you, is [the land] not looted in your hands, is it not [written] (Deuteronomy 2:23), 'the Kaftorim that came out of Kaftor destroyed them and dwelt in their place.'
The world and its fullness [belong to] the Holy One, blessed be He: when He wanted, He gave it to you; when He wanted, He took it from you and gave it to us. That is what is written (Psalms 111:6), 'to give them the inheritance of the peoples,' [and so, it is stated in the first part of the verse,] 'The strength of his actions He told His people.'" [This means that, in order to give them the inheritance of the nations, He told them [about the] beginning. And the matter that I mentioned has already come from another source: about the hidden matters of the story of creation, our Rabbis, of blessed memory, have said (Psalms 111:6), "'The strength of his actions He told His people;' to tell the strength of the story of creation to flesh and blood is impossible. Therefore, the verse is sealed to you [and only states], 'In the beginning, God created." If so, what we said about this is elucidated.
How is it that the children of Israel will not be spewed out by the Land like the Canaanites? It is by the Renewing of the Covenant that God made with Avraham.
This is the covenant of the Pasover Lamb renewed in Yehoshua HaMashiach. There is no other entitlement to the Land of Israel. World without end. As it was in the beginning, is now and ever shall be. Amen.