Forty days after Easter Day, Jesus went up, or "ascended," into heaven; and our Church keeps that day holy, and calls it "The Ascension Day," because "ascension" means going up.
For ten days after the Ascension, the disciples, who had seen their Lord ascend, remained quietly at Jerusalem, praising God for all that had been done, and praying continually both in private and in public. Another great feast of the Jews was now drawing near: this feast is spoken of under different names in the Old Testament, and we must now say something about it.
In the Law of Moses, the Jews were, as has already been said, commanded to offer up a sheaf of corn on the day after the Sabbath which followed the Feast of the Passover; that is, on the first day of the week, after the Passover week. This sheaf was offered up as a thank-offering at the beginning of harvest, for they began to cut the barley (the first corn crop) immediately after the Passover.
Seven weeks after this beginning of harvest, the Jews were to keep one of the three great feasts, ordained by the Mosaical, or Levitical Law. This great feast was called "The Feast of Weeks," because it was observed seven weeks after that of the Passover: seven weeks were called "a week of weeks," because seven days make a week, and there were seven times seven days in the Feast of Weeks. It was also called "The Day of First Fruits," because it was then the time to begin to gather in the other crops and productions of the ground; and in thankfulness for all these fruits of the earth, a new meat offering was offered unto the Lord.
The Jewish Rabbis also called this great feast, "The Day of the Giving of the Law," because the Law was given by God to Moses on Mount Sinai, fifty days after the Children of Israel ate the first Passover in Egypt; and this feast, as we have said, was kept on the fiftieth day after the Feast of the Passover. In the New Testament this feast day is called "The Day of Pentecost": because in Greek, "Pentecost" means fiftieth, and as we have said, the Jews were to number fifty days from the morrow after the Passover Sabbath, and then to keep this great feast.
As Jesus rose on the morrow after the Passover Sabbath, our Easter Day (or Easter Sunday), the fiftieth day, would again be on the first day of the week, Sunday with us: seven weeks or fifty days from the blessed day on which our Lord rose from the grave, and ten days after His Ascension.
This Day of Pentecost, distinguished already as a day of rejoicing and thanksgiving for many blessings, temporal and spiritual, and called "The Feast of Weeks," "of First Fruits," and of "The Giving of the Law," was now chosen by God as the day on which the promised gift of the Holy Spirit was to be poured out upon the Apostles, to their great spiritual benefit, as well as to that of all who were to look to their teaching, for the knowledge of what Jesus Christ has done for sinners.
We read in the Book of Acts, "And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them." Fire was looked upon by the Jews as a sign of the presence of God. And those upon whom these tongues of fire descended, were at once "filled with the Holy Ghost": a visible and miraculous sign immediately followed, for they "began to speak with other tongues," that is, in strange and foreign languages, which they had never learnt, "as the Spirit gave them utterance."
Thus were accomplished the promises of Jesus, to send the Comforter upon His Apostles, and that they should be baptized with the Holy Ghost.
The power of speaking strange languages was a most valuable gift, enabling the Apostles to obey the command "to teach all nations," which they could not have done had they not been able to make themselves understood by all men.