The beginning of the book follows a conventional opening statement containing the name of the addressee, Theophilus, and a brief reminder of the content of the "former account" by the same author.
Verses 1–3
"Former account" : refers to Gospel of Luke.
"Theophilus" : the intended reader of this book, as well as the previous one, might be a "patron" who is already informed about "things which have been fulfilled among us", but still needs "assurance" to "know the certainty of those things".
This section records that forty days after the resurrection, Jesus commands the disciples during a meal to await the coming of the Holy Spirit, then a cloud takes him upward from sight, and two men in white appear to tell them that he will return "in the same way you have seen him go into heaven."
Verse 8
Before Jesus left, he charged the disciples with the task of acting as 'witnesses' to him, in the locations that can be read as a 'geographical program' for the whole book of Acts:
The first 7 chapters set in Jerusalem
Chapter 8—11 record the spread of the gospel to the surrounding areas within Syria-Palestine
Chapter 13 onwards following Paul's mission ever farther places.
Luke chapter 24 tells how Jesus leads the eleven disciples "as far as" Bethany, a village on the Mount of Olives, where he instructs them to remain in Jerusalem until the coming of the Holy Spirit: "And it came to pass, while he blessed them, he parted from them, and was carried up into heaven. And they worshiped him, and returned to Jerusalem with great joy". The Gospel of John has three references to ascension in Jesus' own words: "No one has ascended into heaven but he who descended from heaven, the son of man" ; "What if you were to see the son of man ascending where he was before?" ; and to Mary Magdalene after his resurrection, "Do not hold me, for I not yet ascended to my father...". Various epistles also refer to an ascension in relation to the post-resurrection "exaltation" of Jesus to the right hand of God. Gospel of Mark contains the brief ascension account, but it is considered by a broad consensus among scholars to be a later addition to the original version of that gospel.
Verse 12
"The hill called the Mount of Olives" : This geographical site is mentioned by Luke alone in the narrative of Jesus' last entry into Jerusalem and as a place to rest during Jesus' final ministry of teaching. names Bethany as the site of ascension, which is identified in as a location at the Mount of Olives.
"A Sabbath day's walk" : 2000 cubits, about 5/8 mile or about 1 kilometer, showing a proximity to Jerusalem, as well as portraying the disciples as faithful Jews. The distance seems differ significantly with the Bethany in, but the ascension site, according to Lightfoot, "was from the place where that tract of the Mount of Olives ceased to be called Bethphage and began to be called Bethany", not inside the village.
As the disciples waited obediently in the upper room in Jerusalem for the promised coming of the Holy Spirit, they devoted themselves "with one accord" in prayer, underlying the unity of the group which surprisingly now includes Jesus' mother, brothers, and some women. Verse 13 lists the names of the apostles with some differences compared to the apostolic list in :
Andrew was moved down from the second place to the fourth place after John
Thomas was moved up from the eighth place to the sixth place following Philip
The omission of Judas Iscariot motivates the narrative of his final fate and Peter's call to find his replacement. The process begins by Peter's appeal to the Scripture, and the requirements for the candidate. With this, Peter reinforces the identity of the group and exerts his de facto authority in the group.
"Brothers": or "brothers and sisters", translated from the plural Greek word adelphoi, which, depending on the context in New Testament usage, may refer either to "brothers" or to "brothers and sisters".
Verse 15
"Stood up": from Greek: ἀναστὰς: adding a participle to a finite verb to indicate the posture or position of a speaker is a characteristic of Luke as this word is found in the Gospel of Luke 17 times, and in Acts 19 times, only twice in Matthew, six or seven times in Mark.
Verses 21–22
"Went in and out": is a "Semitism or Septuagintalism" expression, comparable to the English phrase "comings and goings".
"Beginning" : The "baptism" of John" to "that day when He was taken up from us" mark the scope for the story of Jesus, with an emphasis on "His resurrection". In Acts 10, Luke notes Peter preaching the gospel using "precisely the same parameters" also using arxamenos with the claim of being a witness specifically to the resurrection.
The apostles proceeds by asking God as the only resource to 'indicate' his choice through the casting of lots, which is a familiar mean to ascertain divine purpose in both the Graeco-Roman world and the Bible, to get Matthias "numbered with the eleven apostles".
