God’s purpose for the gift of tongues was three-fold.
Sign of authority.
Being one of the miraculous sign gifts, it confirmed the authority of the Apostles. The Apostles were used to give new revelation to the newly formed church. Since the New Testament had not yet been written, signs and wonders accompanied their teaching to authenticate them and their message (Acts 2:42-43).
Sign of blessing.
The sign gift of tongues showed to the Jews that other groups were included in the