This was something Peter said out of his own will before the Holy Spirit was upon Him. Peter had been wrong before. The Holy Spirit baptized him in the following chapter leading up to his spirit-led leadership of the church.
That could be argued from John 20:22
When He had said this, He breathed on them and said, “Receive the Holy Spirit.
Mathias didn’t yet or the other men also present in the upper room, but the eleven