When the apostle on the Pentecost day gathered together in the upper room waiting for the promise ( Act 2:1). Suddenly, there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting (Act 2:2).
There appeared to them divided tongues, as of fire, and one sat upon the apostle. (Act 2:3).
And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance (Act 2:4).
Verse 4 describes how they began to speak in tongues as the Holy Spirit gave them utterance. This affirms that when we speak in tongues, the Holy Spirit pray with our spirit, granting it utterance just as He did for the apostles. Prior to the Holy Spirit coming upon them, the apostles were unable to speak in tongues because no such utterance was given.