life (see John 3:5-6). The Holy Spirit gives power to believers so they can serve Christ (Acts 1:4,8). After his resurrection, Jesus told his disciples to wait for the promise of the Father (the promised Holy Spirit. So the disciples gathered together in Jerusalem, and waited. On the Day of Pentecost, the Holy Spirit came upon them--they were baptized in the Holy Spirit (see Acts 1:5; 2:4). As evidence of this miracle, the believers began to speak in tongues. Jews from various parts of the world were at Jerusalem for the Feast of Pentecost. As the believers spoke in tongues, the Jews understood them in their various languages. So the Pentecostal tongues were intelligible by all those listening. In contrast, the tongues spoken later by the Corinthian Church were not intelligible to everyone, but only to those with the spiritual gift of interpretation of tongues (see 1 Corinthians 14:27,28).
