Speaking in tongues, also known as glossolalia, is mentioned in several places in the Bible, primarily in the New Testament.  Acts 2:1-4 – This passage describes the event of Pentecost where the Holy Spirit descended upon the apostles, and they began to speak in other tongues as the Spirit gave them utterance. This is one of the most direct references to speaking in tongues in the Bible. When the day of Pentecost came, they were all together in one place. Suddenly a sound like the blowing of a violent wind came from heaven and filled the whole house where they were sitting. They saw what seemed to be tongues of fire that separated and came to rest on each of them. All of them were filled with the Holy Spirit and began to speak in other tongues as the Spirit enabled them. 1 Corinthians 14 – This entire chapter is a good resource for understanding the use and purpose of speaking in tongues within the church. Paul discusses how speaking in tongues is a spiritual gift and should be used for the edification of the church, especially when interpreted. Follow the way of love and eagerly desire gifts of the Spirit, especially prophecy. For anyone who speaks in a tongue does not speak to people but to God. Indeed, no one understands them; they utter mysteries by the Spirit. Mark 16:17 – In this passage, Jesus mentions speaking in new tongues as one of the signs that will accompany those who believe. And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues. Acts 10:44-46 – This passage describes how the Holy Spirit fell on all who heard the word at Cornelius’ house, and they began speaking in tongues and praising God. While Peter was still speaking these words, the Holy Spirit came on all who heard the message. The circumcised believers who had come with Peter were astonished that the gift of the Holy Spirit had been poured out even on Gentiles. For they heard them speaking in tongues and praising God. Acts 19:6 – When Paul placed his hands on them, the Holy Spirit came on them, and they spoke in tongues and prophesied. When Paul placed his hands on them, the Holy Spirit came on them, and they spoke in tongues and prophesied. These passages provide a biblical foundation for the practice and understanding of speaking in tongues within Christian theology.