John Calvin Commentary Acts 2:1

"And when the day of Pentecost was now come, they were all together in one place." — Acts 2:1 (ASV)

And when. To be fulfilled is understood here to mean to come. For Luke testifies again to their perseverance when he says that they all remained in one place until the time appointed for them. The adverb with one accord supports this. Furthermore, we have previously explained why the Lord deferred sending His Spirit for a whole month and a half.

But the question is why He sent Him primarily on that day. I will not refute Augustine's profound and subtle interpretation: that just as the Law was given to the people of old fifty days after Easter, written on tablets of stone by the hand of God, so the Spirit, whose office it is to write the Law in our hearts, fulfilled what was prefigured in the giving of the Law an equal number of days after the resurrection of Christ, who is the true Passover.

However, while Augustine urges this subtle interpretation of his as necessary in his book Questions on Exodus and in his Second Epistle to Januarius, I would wish him to be more restrained and modest in this matter. Nevertheless, let him keep his own interpretation to himself. Meanwhile, I will embrace what is more sound.

This miracle was performed on the feast day, when a great multitude customarily gathered in Jerusalem, so that it might be more widely known. And truly, as a result, news of it was spread abroad, even to the farthest parts of the earth.

For the same reason, Christ often went up to Jerusalem on the holy days (John 2; John 5; John 7; John 10; John 12) so that the miracles He performed might become known to many, and that among the larger gathering of people His teaching might bear greater fruit.

Similarly, Luke will later declare that Paul hurried to reach Jerusalem before the day of Pentecost, not for the sake of religious observance, but because of the larger assembly, so that he might achieve more (Acts 20:16).

Therefore, in choosing the day, the benefit of the miracle was considered: first, so that it might be more highly praised in Jerusalem, because the Jews were then more inclined to consider the works of God; and secondly, so that it might be proclaimed abroad, even in distant lands.

They called it the fiftieth day, counting from the offering of the first-fruits.