The Bible reveals no disagreement between Jesus or His apostles and the Jews about whether the festivals are to be kept. Indeed, the subject is approached assuming they will be kept. W.J. Conybeare and J.S. Howson confirm the early New Testament church kept them:
The festivals observed by the Apostolic Church were at first the same with those of the Jews; and the observance of these was continued, especially by the Christians of Jewish birth, for a considerable time. A higher and more spiritual meaning, however, was attached to their celebration. . . . (The Life and Epistles of St. Paul, p. 346)
Referring to the apostle Paul, they write, "Nay more, he himself observed the Jewish festivals" (p. 574).
The Bible plainly shows Jesus observing the Feast of Tabernacles and Last Great Day with the Jews in John 7. In John 11:55-57, the Jews standing in the Temple question whether He would come to the Feast, as though this would break a customary habit. Regarding Pentecost, some feel that the Bible records Jesus keeping it with the Jews, apparently in agreement as to the proper day, in Luke 4:16. This is the Sabbath on which Jesus, in His hometown, formally states the purpose of His ministry.
Luke does not say it is Pentecost, just that it is a Sabbath He customarily kept. The evidence derives from what He read from the Scriptures. According to the Jewish Encyclopedia, under the article "Triennial Cycle" (a three-year plan for the public reading of the Old Testament, attributed to Ezra), the portion of the Law to be read on Pentecost in the second year of the cycle (AD 28) is Exodus 20. The Pentecost reading from the Prophets is the very section Christ reads, Isaiah 61:1-2! A Jewish Quarterly Review article, "The Reading of the Law and Prophets in a Triennial Cycle," by Dr. Adolf Büchler (Vol. IV, October 1893, pp. 1-73) confirms this fact. Remember, His ministry was three-and-a-half years long. He was crucified in the spring of AD 31, so this Sabbath (possibly Pentecost) would have occurred shortly after He began His ministry.
Stronger yet is the evidence from Acts 2 that the newly forming Christian church was sharing the day of Pentecost with the Jews in Jerusalem. Acts 2:1 states that this occurred on the day of Pentecost. Furthermore, verse 5 calls the Jews who witnessed the Pentecost occurrences "devout." The Christians and Jews are in the same general area for religious reasons.
In addition, verses 7-11 say that visitors had traveled from other areas, both Jews and proselytes. Here is a typical comment:
Certain "God-fearing Jews" who were residing in Jerusalem from many parts of the Diaspora, together with a number of Jews and proselytes who had returned to Jerusalem as pilgrims for the Pentecost festival, were "in bewilderment," "utterly amazed," and "perplexed" by the miraculous coming of the Spirit (vv. 6-7, 12). (Expositor's Bible Commentary, vol. 9, p. 272)
Where does this activity take place? No one can pinpoint with absolute certainty the exact location. The final verse of Luke records briefly what the apostles did after Jesus' ascension: "[They] were continually in the temple praising and blessing God" (Luke 24:53). We find them in Acts 1:13 in the "upper room" somewhere in Jerusalem. Acts 2:2 mentions them being in a house when the Pentecost miracles begin. The house and upper room are likely the same place and probably near the Temple where devout people would assemble, especially on a festival day.
Concerning Acts 2:6, Expositor's Bible Commentary says: "The verb for 'hear' (ekouon) is in the imperfect tense, suggesting that their hearing took place over a period of time—perhaps first in the upper room itself, then in adjacent lanes and courtyards, and finally in the temple precincts" (vol. 9, p. 272).
Acts 20:16 shows the apostle Paul "hurrying to be at Jerusalem, if possible, on the Day of Pentecost." He apparently made it, for Conybeare and Howson conclude that the episode involving Paul and the four men under a vow (Acts 21:23-26) occurred on Pentecost (p. 574). Finally, Paul states before the Jewish leaders in Rome, "Men and brethren, though I have done nothing against our people or the customs of our fathers . . ." (Acts 28:17). "Customs" includes festivals.
The internal evidence from the Bible and from religious researchers confirms that Jesus, the Christian church, and the Jews who were responsible for setting the festival dates agreed on when Pentecost and the other festivals should be observed (except the well-documented Passover difference).