As with the other feast and holy days, Pentecost has many lessons to teach.
Many people outside the Church of God do not understand why God requires that we observe the holy days. But God is in the business of shaping our character and teaching us lessons. God is the great Teacher, and He uses physical means to teach spiritual lessons. Each feast and holy day can teach us lessons.
One of the lessons of Pentecost is that only the first fruits are being called to salvation in this age, and that in turn teaches the lesson of hierarchy in God's kingdom.
The majority of mankind is not being called to salvation at this time. God is not trying to save or convert the world right now. He wants mankind to experience the full effect of Satan's way of life for 6,000 years so there will be no doubt that Satan's way does not work.
But God is calling a few now to salvation to prepare them to rule the earth with Christ in the millennium and beyond. Those few are us, those in God's true Church.
We have a harder test and trial than the majority of mankind will have when their opportunity for salvation comes during the millennium or the white throne judgment period. We have to overcome Satan now in this life, but Satan will be put away at the beginning of the millennium, and those who are called later will not have to struggle against his influence as we do.
But we who overcome Satan in this life, the first fruits represented by Pentecost, will also have greater rewards and higher positions in the kingdom of God. We will rule with Christ on His throne.
"And he who overcomes, and keeps My works until the end, to him I will give power over the nations" (Revelation 2:26).
"To him who overcomes I will grant to sit with Me on My throne, as I also overcame and sat down with My Father on His throne" (Revelation 3:21).
"So Jesus said to them, 'Assuredly I say to you, that in the regeneration, when the Son of Man sits on the throne of His glory, you who have followed Me will also sit on twelve thrones, judging the twelve tribes of Israel' " (Matthew 19:28).
"Then came the first, saying, 'Master, your mina has earned ten minas.' And he said to him, 'Well done, good servant; because you were faithful in a very little, have authority over ten cities.' And the second came, saying, 'Master, your mina has earned five minas.' Likewise he said to him, 'You also be over five cities' " (Luke 19:16-19).
There will be hierarchy and organization in the kingdom of God. We will not all be at the same level of authority. The Church is a model. Just as there are different positions or ranks of authority in the Church (Ephesians 4:11-17, 1 Corinthians 12:27-28), so it will be in the kingdom of God.
Pentecost, by teaching us that there are first fruits today who will rule over mankind in the millennium, is a reminder of the lesson of hierarchical government and organization in God's kingdom.
Here are links to related chapters or sections in Preaching the Gospel:
Pentecost - the Gift of the Holy Spirit, Chapter 2