1The first book I wrote, Theophilus, concerned all that Jesus began both to do and to teach, 2until the day in which he was received up, after he had given commandment through the Holy Spirit to the apostles whom he had chosen. 3To these he also showed himself alive after he suffered, by many proofs, appearing to them over a period of forty days and speaking about God’s Kingdom. 4Being assembled together with them, he commanded them, “Don’t depart from Jerusalem, but wait for the promise of the Father, which you heard from me. 5For John indeed baptized in water, but you will be baptized in the Holy Spirit not many days from now.”
6Therefore, when they had come together, they asked him, “Lord, are you now restoring the kingdom to Israel?”
7He said to them, “It isn’t for you to know times or seasons which the Father has set within his own authority. 8But you will receive power when the Holy Spirit has come upon you. You will be witnesses to me in Jerusalem, in all Judea and Samaria, and to the uttermost parts of the earth.”
9When he had said these things, as they were looking, he was taken up, and a cloud received him out of their sight. 10While they were looking steadfastly into the sky as he went, behold, two men stood by them in white clothing, 11who also said, “You men of Galilee, why do you stand looking into the sky? This Jesus, who was received up from you into the sky, will come back in the same way as you saw him going into the sky.”
12Then they returned to Jerusalem from the mountain called Olivet, which is near Jerusalem, a Sabbath day’s journey away. 13When they had come in, they went up into the upper room where they were staying, that is Peter, John, James, Andrew, Philip, Thomas, Bartholomew, Matthew, James the son of Alphaeus, Simon the Zealot, and Judas the son of James. 14All these with one accord continued steadfastly in prayer and supplication, along with the women and Mary the mother of Jesus, and with his brothers.
15In these days, Peter stood up in the middle of the disciples (and the number of names was about one hundred twenty), and said, 16“Brothers, it was necessary that this Scripture should be fulfilled, which the Holy Spirit spoke before by the mouth of David concerning Judas, who was guide to those who took Jesus. 17For he was counted with us, and received his portion in this ministry. 18Now this man obtained a field with the reward for his wickedness; and falling headlong, his body burst open and all his intestines gushed out. 19It became known to everyone who lived in Jerusalem that in their language that field was called ‘Akeldama,’ that is, ‘The field of blood.’ 20For it is written in the book of Psalms,
‘Let his habitation be made desolate.
Let no one dwell in it;’
and,
‘Let another take his office.’
21“Of the men therefore who have accompanied us all the time that the Lord Jesus went in and out among us, 22beginning from the baptism of John to the day that he was received up from us, of these one must become a witness with us of his resurrection.”
23They put forward two: Joseph called Barsabbas, who was also called Justus, and Matthias. 24They prayed and said, “You, Lord, who know the hearts of all men, show which one of these two you have chosen 25to take part in this ministry and apostleship from which Judas fell away, that he might go to his own place.” 26They drew lots for them, and the lot fell on Matthias; and he was counted with the eleven apostles.
For a number of reasons, neither the location of the Upper Room (whether the traditional location on Mt. Zion) nor the Syrian Church (in the Armenian Quarter of the Old City) are likely sites for the events that are observed on the day of Pentecost.
First, the location inside an upper room would not have provided an adequate setting for people in the street to observe the events mentioned in Acts 2. The room would have been within the very limited space for a very large crowd from the Diaspora and Judea to gather to observe the miraculous sights and hear Peter's sermon or for an interchange between Peter and the crowds in the street below.
Second, the text also does not say that the event was in the Upper Room (the eleven are only mentioned in Acts 2:14), but that they, that is, the apostles were of one accord (the Greek grammar and context of Acts 1 and 2 indicate the apostles and not the 120 people).
Third, The events of the Upper Room probably occurred in the evening (where the apostles and a few other believers ate and slept) rather than in the daytime. The coming of the Spirit seems to be in the daytime (Peter said the third hour of the day, or 9:00 a.m.), near the mikveh (baptismal pools) at the southern end of the temple mount, where thousands were baptized that day. The most likely location for the events in Acts is in Solomon's Portico at the southern end of the Temple Mount, approximately the location presently known as the Al Aqsa Mosque. This is in agreement with Luke's statement in Luke 24:52-53 (daily they were in the temple, waiting for the Spirit to come), and also the size of the crowds necessary for the narrative in Acts 2 of the multitude observing the coming of the Holy Spirit, as well as the response of thousands following Peter's sermon (Acts 2:41) for baptism.