What theme is emphasized in the book of Acts regarding speaking in tongues?

The emphasis on speaking in tongues in the book of Acts is primarily tied to its role as a sign for all believers. In the context of Acts, speaking in tongues serves as a manifestation of the Holy Spirit's presence and is intended to facilitate communication, especially during significant moments like the Pentecost. The outpouring of the Holy Spirit upon the apostles resulted in the ability to speak in various languages, which allowed them to share the gospel effectively with a diverse audience. This event highlights the inclusivity of the message of Jesus and demonstrates that the Holy Spirit empowers all believers, not just a select few. Thus, speaking in tongues is portrayed as a universal sign of the Spirit’s work in the life of the church, affirming its significance for all who believe.