Pentecost Experience

Acts 2. The coming of the Holy Spirit at Pentecost marks the official inauguration of the new covenant and serves as a witness to the nation of Israel. The Church’s reception of the Holy Spirit, preaching, and sudden growth testify to the reality of Christ’s resurrection and His ongoing reign.

It was when the day of Pentecost was fully come, that is, the night preceding, with a part of the day, was fully past. This was a Jewish feast held 50 days after Passover. It celebrates the first fruits of the wheat harvest. It was now 10 days after the time Jesus ascended to heaven (Acts 1:3); Jesus had commanded them to wait for the coming of the Holy Spirit. 

The Holy Ghost came down at the time of a solemn feast; there was then a great crowd of people to Jerusalem from all parts of the country, and the proselytes from other countries, which would make it the more public, and the fame of it to be spread the sooner and further, which would contribute much to the propagating of the gospel into all nations.  

This feast of Pentecost happened on the first day of the week, which was an additional honor, and a confirmation of it to be the Christian sabbath, the day which the Lord hath made, to be a standing memorial in his church of those two great blessings – the resurrection of Christ, and the pouring out of the Spirit, both on that day of the week. This serves not only to justify us in observing that day under the style and title of the Lord’s day, but to direct us to give God praise particularly for those two great blessings every Lord's day in the year, with prayers and praises.

Matthew Henry Commentary on the Whole Bible.