The Day of Pentecost is two things. First, it is the birth of the Christian church. Admittedly, the church that began then was considerably different than the church we see now but they are connected in an unbroken chain. Second, it was a new manifestation of the Holy Spirit. It was a new manifestation, not a new Holy Spirit.
It can be a challenge for us to remember a couple of things about the Holy Spirit, at least a couple. We need to remember that the Holy Spirit is a person–not an impersonal force, not something akin to radiation, but a person. We also need to remember the Holy Spirit is part of the Trinity and has always been. The Holy Spirit did not spring into existence at Pentecost but has always existed.
The sermons explore these things and a few others and look at their implications for us. I spend some time talking about pronouns for the Holy Spirit, namely “they,” and “she.” I spend more time talking about what it means to be in a relationship with God through Jesus empowered by (this) Holy Spirit.
As always, let me know what you think.