Presumably the coming of the Holy Spirit was seen in a visible manner and then confirmed also by the actions of the Gentile believers. Since they were most likely Greek speakers, they may have begun to speak in Hebrew and Aramaic.1 It would have been a joy to hear the Gentiles praising God for his work in Christ in the language that Peter and the other circumcised believers knew well.
46 For they were hearing them speaking in tongues and extolling God. Then Peter declared,