English Standard Version (ESV)
To think those Jews had no idea what was in store for them when they gathered. Some probably had high expectations for the festival, but none expected anything like Pentecost. This was a new thing, and God had gathered a crowd to take an active role, even though they surely didn't expect sure miracles.
This is the role of the church. We are to show up, ready to worship but also ready for God to do a new thing, for God to reveal a new course for us to chart. We have a role of active listening -- we can't be so certain of what will happen that we block out any room for God to do the unexpected. This is why we have Sabbath - so we can devote ourselves to attending to what God has to say to us. We aren't merely following a rut -- God is at work, and it's up to you and I to show up, every day, with hearts ready to be inspired by the work of the Holy Spirit among and within us.