And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions:
And also upon the servants and upon the handmaids in those days will I pour out my spirit. And I will shew wonders in the heavens and in the earth, blood, and fire, and pillars of smoke.
Joel 2:28-29
In the Old Covenant, only the prophets a Kings had the promised Holy Spirit. The Lord appointed and anointed a few, and those chosen vessels fulfilled His promise in the Earth.
To contrast this, God spoke by the prophet Joel that the day would come when God would pour out His Spirit on all flesh, meaning, no longer the select few, but to as many who would believe. The promise, of course, does not apply to a non-believer, but merely those who would come to salvation.
Peter, under the unction of the Holy Spirit, correctly interpreted the application of this scripture to the outpouring of the Spirit on the day of Pentecost (In Acts 1:6, the disciples asked when the Kingdom would be restored to the nation as a whole, something that has not yet occurred. See here for more on that question).
The Kingdom of God was there from the beginning, but it was only accessible to a select few. Those who God chose had access to the government and dominion of God, and Israel, through the tabernacle of Moses, were able to participate in God’s plan and design, His pattern which was Christ, but it was only in the New Testament when everyone could both see and enter the Kingdom of God (John 3:3-5).