Sunday mornings, we are studying the book of Acts. It's an elementary school-age Sunday School class.
A couple Sundays ago we made it to Peter's sermon in response to the crowd that was responding to the Holy Spirit arriving at Pentecost.
Peter begins by explaining the prophet Joel told us long ago that what was happening would happen.
I told the students that Peter was quoting Joel, and I had them look at both Acts 2:17-21 and Joel 2:28-32.
Upon reading the same thing in both places, one of the students exclaimed, "Wait, they're the same!"
Yes, they're the same. That's what I meant when I said Peter was quoting Joel!
The New Testament is built on the Old Testament.