What does Acts 4:4 mean?

Peter and John spent the afternoon explaining to people that they were able to heal a lame man through the power of Jesus of Nazareth whom the Jews crucified. But Jesus rose again and, if the people repent, He will forgive their sins (Acts 3). The priests and Sadducees, who don't believe anyone can rise from the dead, arrest Peter and John. But they're too late. Many of the men, not to mention women, believe Peter's message, accept Jesus as their Savior, and receive the Holy Spirit.

Jesus had told His disciples that they would be His "witnesses in Jerusalem and in all Judea and Samaria, and to the end of the earth" (Acts 1:8). They are in the middle of their ministry in Jerusalem. Before long, persecution will rise, the believers will flee Jerusalem, and the persecuted church will spread the story of Jesus throughout Judea and Samaria (Acts 8:1–3).

For now, the church in Jerusalem is growing. After Peter's first sermon, right after receiving the Holy Spirit, three thousand Jewish travelers, in Jerusalem for Pentecost, came to faith in Jesus (Acts 2). Since then, "the Lord added to their number day by day those who were being saved" (Acts 2:47). It will continue. The five thousand mentioned probably means the total number of men in the church including those who came because of Peter's sermon here. Counting the women, the number is even larger.

The apostles will continue to preach and heal on the TTemple Mount, and people will continue to believe (Acts 5:12–16). Even after the Sanhedrin flogs the apostles (Acts 5:40), several priests will break ranks and come to the faith (Acts 6:7). By the time persecution scatters the church members, there will be more than enough voices to spread Jesus' message to Judea, Samaria, and beyond.