What is the Kingdom in this verse? Jesus referenced the kingdom earlier in Matthew 6:10, “Thy Kingdom come, Thy will be done on earth as it is done in heaven.” Jesus was teaching an earthly salvation (for mankind) as well as a heavenly salvation (for His followers who make a covenant by sacrifice).
Two salvations were pictured in the Abrahamic promise. God said, "Because you…have not withheld your son, your only son, indeed I will greatly bless you, and I will greatly multiply your seed as the stars of the heavens and as the sand which is on the seashore . . . in your seed all the nations of the earth shall be blessed," Genesis 22:16-18. Abraham’s seed would comprise the stars of heaven (heavenly class) and the sand of the seashore (earthly class). (See also Genesis 26:4,5 and 28:13,14.)
Jesus stated in John 8:56, “Your father Abraham rejoiced to see my day: and he saw it, and was glad.” Obviously, Abraham was long dead, but because of the promise, he did see with the eye of faith. He believed God’s promises would be fulfilled. As stated in Romans 4:3, 9, and 22, “Abraham believed God, and it was counted unto him for righteousness.”
In Hebrews 11, the Apostle Paul reviews the great faith of many Old Testament men and women. He ends by saying, “And all these, having gained approval through their faith, did not receive what was promised, because God had provided something better for us (“stars of heaven” class), so that apart from us they (part of “sand of the seashore” class) would not be made perfect.” This clearly shows they will live again with the help of the “stars of heaven” seed class. Then all the peoples of the earth will be blessed.
When ALL are resurrected (John 5:28-29), God’s truth will cover the earth as the waters cover the sea. (Isaiah 11:9, Jeremiah 31:34) The willing and obedient of mankind will receive perfect, eternal, human life on earth. The founding “fathers” of the faithful – Abraham, Isaac, and Jacob – will be made “princes in all the earth” as stated in Psalm 45:16.
They will work as the earthly governors and counselors of Christ’s kingdom. Isaiah 2:2-3, “And it shall come to pass in the last days, that the mountain of the LORD'S house shall be established in the top of the mountains…and all nations shall flow unto it. And many people shall go and say, Come ye, and let us go up to the mountain of the LORD, to the house of the God of Jacob; and he will teach us of his ways, and we will walk in his paths: for out of Zion shall go forth the law, and the word of the LORD from Jerusalem.” What a wonderful promise yet to be fulfilled!