Isaiah 60:21: “they shall inherit the land for ever”
Isaiah 60:21 says, “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.”
Revelation 21 is based upon Isaiah 60. Both chapters describe the blessings of the church, the New Jerusalem. Does the church inherit the land? What land is it?
Bastow’s biblical dictionary says: 
The Hebrew term adamah, rendered “earth,” merely designates a portion of the earth’s surface; (Gen. iv. 11; vi. 1; vii. 4;) a “land” or country. (Gen. xxviii. 15; Isa. xiv. 2; Ps. xlix. 11.) So also the term eretz, translated “earth,” generally denotes a land, country, region, a portion of the habitable earth; (Gen. xxi. 82; xxvi. 3, 4; Ex. iii. 8; xiii. 6;) as opposed to the sea. (Gen. i. 28.) It is also used for the inhabitants of the earth. (Gen. ix. 19; xi. 1; xix. 31.) When conjoined with the “heavens,” it denotes the whole universe. (Gen. i. 1; ii. 1,4.)
Jesus said, “Blessed are the meek: for they shall inherit the earth.” [Matthew 5:5]
In his commentary on Isaiah Joseph Addison Alexander suggested that the “earth” (eretz) in Isaiah 60:21 has a higher meaning, as a type or a symbol for God’s spiritual creation in the lives of the saints. Alexander wrote: 
21. And thy people, all of them righteous, forever shall inherit the earth, the branch (or shoot) of my planting, the work of my hands, to glorify myself (or to be glorified). Compare ch. 4:2. 33:24. 35:8. 52:1. Rev. 21:7, 27. The first clause may also be read as two distinct propositions, thy people all of them are (or shall be) righteous, forever they shall inherit the earth. According to the literal interpretation, so called, this is a promise that the Jews shall possess the Holy Land forever. But even granting land to be a more literal and exact translation, which it is not, still the usage of the Scriptures has attached to this prophetic formula a much higher meaning, the possession of the land being just such a type or symbol of the highest future blessings as the exodus from Egypt is of ultimate deliverance, or the overthrow of Sodom and Gomorrah of sudden, condign, irretrievable destruction. But in favour of the wider version, earth, is the analogy of ch. 49:8, where Israel is represented as occupying and restoring the desolate heritages of the whole earth.
The context in which eretz or land is used in Isaiah 60:21 is not so much about the extent of the land which the church inherits, as the duration of it, which is forever. This idea of perpetuity is also present in the blessing Joseph received from his father Jacob, in Genesis 49:26. Like Isaac and Abraham, Jacob did not possess the promised land during his lifetime, but he “sojourned in the land of promise, as in a strange country,” [Hebrews 11:9] and they looked for a resurrection. In the blessing Jacob said, “The blessings of thy father have prevailed above the blessings of my progenitors unto the utmost bound of the everlasting hills.” His blessings were high and lofty, or spiritual in nature, and also durable, like the “everlasting hills” in the promised land.
To inherit the land forever, in Isaiah 60:21, means to inherit the spiritual things that the promised land represents. Hebrews 11:16 says, “but now they desire a better country, that is, an heavenly.” This heavenly or spiritual inheritance includes understanding the revelations of God, as well as other gifts of the Spirit, such as those that were present in the early church.
1. James Austin Bastow. A biblical dictionary. 1859. p. 220.
2. Joseph Addison Alexander, Isaiah translated and explained. Volume 2. John Wiley, NY. 1851. pp. 370-371.