Were come in - To Jerusalem.
They went up into an upper room - The word ὑπερῷον huperoōn, here translated “upper room,” occurs only four times in the New Testament: Acts 9:37, “She (Dorcas) was sick and died; whom when they had washed, they laid her in an upper chamber” (see also Acts 9:39); Acts 20:8, “And there were many lights in the upper chamber where they were gathered together.” The room so designated was an upper chamber used for devotion, or as a place where to lay the dead before burial, or occasionally for conversation, etc. Here it evidently means the place where they were assembled for devotion. Luke 24:53 says they were continually “in the temple” praising and blessing God; and some have supposed that the upper room here designated was one of the rooms in the temple. But there is no evidence of that, and it is not very probable. Such a room as that here referred to was a part of every house, especially in Jerusalem; and the disciples probably selected one where they might be together, and yet so retired that they might be safe from the Jews. The expression used in Luke 24:53, “They were continually - διαπαντός diapantos - in the temple,” signifies no more than that this was a frequent or customary resort; they were always in the temple at the usual seasons of devotion, or they were in the constant habit of resorting thither. “Even DeWette allows that there is no discrepancy.”
Where abode - Where were remaining. This does not mean that this was their permanent habitation; but they remained there waiting for the descent of the Holy Spirit.
Peter ... - All the apostles were there which Jesus had at first chosen except Judas, Luke 6:13-16.