What does Acts 1:10 mean?

The disciples are standing outside near Bethany, two miles east of Jerusalem, and they are stunned. Forty days ago, their master Jesus rose from a horrific death on a cross. Now, He has just ascended into heaven. They have their orders: go to Jerusalem and wait for the Holy Spirit (Acts 1:4–5), but for now, they need to take a moment to re-orient their thinking.

The two men who greet them are most likely angels, though the text doesn't say so specifically. That there are two of them goes back to the Mosaic Law. In Deuteronomy 19:15, two witnesses are required for a conviction of the law. When Jesus sent out the disciples to preach, cast out demons, and heal the sick, He did so in twos (Mark 6:7–13). He did so again when He sent out seventy-two of His followers to prepare the towns He planned on visiting (Luke 10:1).

Two angels greeted the women who visited Jesus' tomb on the morning of the resurrection (Luke 24:4), although apparently only one spoke (Matthew 28:2–7; Mark 16:5–7). And when Mary Magdalene told Peter and John that the tomb was empty, they both ran to check (John 20:2–3).

Most of the witnessing in the book of Acts is done by two or more. Paul and Barnabas are together during the first missionary journey (Acts 13—14). On the second, Paul takes Silas and Barnabas takes his cousin John-Mark (Acts 15:39–40). It may be that Athens is the only time Paul ministers alone, as he had to flee Berea without warning (Acts 17:13–34). It's not a bad idea to minister in pairs or small groups. As Solomon said, "And though a man might prevail against one who is alone, two will withstand him—a threefold cord is not quickly broken" (Ecclesiastes 4:12).