Israel does not inherit "the whole earth" in future. Just the land between "the Nile and the Euphrates" (which would be able 10 times the land mass of modern Israel. But to deny that the Promised Land is indeed the Promised Land is to make God a liar.
... they shall inherit the land for ever, the branch of my planting, the work of my hands, that I may be glorified.
And the Gentiles shall come to thy light, and kings to the brightness of thy rising… Then thou shalt see, and flow together, and thine heart shall fear, and be enlarged; because the abundance of the sea shall be converted unto thee, the forces of the Gentiles shall come unto thee… And the sons of strangers shall build up thy walls, and their kings shall minister unto thee: for in my wrath I smote thee, but in my favour have I had mercy on thee. Therefore thy gates shall be open continually; they shall not be shut day nor night; that men may bring unto thee the forces of the Gentiles, and that their kings may be brought... Thou shalt also suck the milk of the Gentiles, and shalt suck the breast of kings: and thou shalt know that I the LORD am thy Saviour and thy Redeemer, the mighty One of Jacob...
The sun shall be no more thy light by day; neither for brightness shall the moon give light unto thee: but the LORD shall be unto thee an everlasting light, and thy God thy glory. Thy sun shall no more go down; neither shall thy moon withdraw itself: for the LORD shall be thine everlasting light, and the days of thy mourning shall be ended. Thy people also shall be all righteous: they shall inherit the land for ever, the branch of my planting, the work of my hands, that I may be glorified. (Isa 60:3,5,10,11,16, 19-21)
Really, In Genesis the following can be read: -
Gen 1:1: - 1 In the beginning God created the heavens and the
earth { הָאָֽרֶץ [hā·’ā·reṣ]}
Gen 12:1: . . . .To an
earth { הָאָ֖רֶץ [hā·’ā·reṣ]} that I will show you.
Gen 12:7: '. . . "To your descendants I will give this earth
{ הָאָ֣רֶץ [hā·’ā·reṣ]}."
Gen 15:7-11: - 7 Then He said to him, "I am the Lord, who brought you out of Ur of the Chaldeans, to give you this
earth { הָאָ֥רֶץ [hā·’ā·reṣ]} to inherit it."
8 And he said, "Lord God,
how shall I know that I will inherit it?"
9 So He said to him, "Bring Me a three-year-old heifer, a three-year-old female goat, a three-year-old ram, a turtledove, and a young pigeon."
10 Then he brought all these to Him and cut them in two, down the middle, and placed each piece opposite the other; but he did not cut the birds in two.
11 And when the vultures came down on the carcasses, Abram drove them away.
Gen 15:17-21: - 17 And it came to pass, when the sun went down and it was dark, that behold, there appeared a smoking oven and a burning torch that passed between those pieces.
18 On the same day the Lord made a covenant with Abram, saying:
"To your descendants I have given this
earth { הָאָ֣רֶץ [hā·’ā·reṣ]}, from the river of Egypt to the great river, the River Euphrates —
19 the Kenites, the Kenezzites, the Kadmonites,
20 the Hittites, the Perizzites, the Rephaim, 21 the Amorites, the Canaanites, the Girgashites, and the Jebusites." Source: - biblehub.com
In Genesis 12:1 God promises to give to Abraham the earth that He, God, would show Abraham, What is the earth that God will show Abraham? An earth that is to be filled with righteousness, not like the fallen earth that Abraham was living in.
Now in Genesis 1:1
hā·’ā·reṣ is translated as earth, whereas in the other four verses quoted above this transliterated word has been translated as "land" whereas a better understanding of God's promises to Abraham makes more sense if this transliterated word is also translated as "earth." Genesis 15:17-20 is God's response to Abraham's question of, "how shall I know that I will inherit it, i.e. the earth?" God response is to tell Abraham that He will give his descendants the following area of land, on the fallen earth but God provides no indication as to how long the land will remain in their possession. We know from scripture, that during Solomon's reign that Israel had dominion over the land as described in Genesis 15:18-20 but that soon passed from Israel's grasp.
Now you quoted
Isaiah 60:21 and the key portion of this verse is best translated as: -
Also your people shall all be righteous;
They shall inherit the earth { אָ֑רֶץ [’ā·reṣ]} forever,
The branch of My planting,
The work of My hands,
That I may be glorified.
Perhaps before you begin to admonish me for making God a liar, concerning my understanding of God's promises to Abraham and his descendants, that you might like to do a little more digging into God's word to establish whether or not I what I see is at all possible. Yes, Gen 15:18-20 has been labelled the promised land, but God's promise to Abraham is that he and his descendants will inherit the whole righteous earth that God will show them.
God's focus is not on a physical possession but in a spiritual change in Abraham and his descendants such that the earth that God will show then, still in our distant future, is an earth based on righteousness that will be filled by people who God judges righteous and worthy to receive the earth as their inheritance.
Shalom
