Speaking in tongues is the evidence of the infilling of the Holy Ghost/Spirit. The word is clear on that topic even though many reject it.
I know this to be true because of the word, and secondly because of my personal experience that aligned with the word:
I received the baptism of the Holy Ghost and spoke in tongues when I was very young. Years later I got water baptized "in the name of the Father, Son and Holy Ghost." Afterward, upon seeing that all recorded water baptisms were done in the name of the Lord Jesus I was water baptized that way. For me, personally, afterward my spiritual eyes were indeed open. (John 3:3) I could "see" (understand) scriptures with greater clarity than in the past.
During prayer, my language changes to tongues as well at times when I am singing.
About ten years later, God imparted the Spiritual gift of tongues upon me that was interpreted by another for edification of the church body. I had not been seeking the gift, however, while praising God in the worship service He decided to flow through me and speak a message to the congregation.
As I was praising God I could feel His presence stronger than in times past; so strong in fact, I sensed something was definitely different but had no idea what was going on. As I praised the Lord someone to my left began to speak in tongues. I remember thinking Lord if that is what you wanted me to do I would have done it. Immediately the individual stopped speaking. I felt what can only be described as an internal explosion; a feeling of complete fullness that my body could not contain. To my utter dismay the fullness began pouring out in the form of tongues. There I was, normally the shy, quiet one, loudly proclaiming half of a message that was afterward interpreted. I say half, because the interpretation began and part way through the message there was a distinct pause. The proclaimed message began with the other individual and was picked up and concluded through me.
On the drive home I could not help re-living the incident over, and over in my mind. I was amazed at what had occurred. I questioned the Lord about the explosive feeling. His answer was not audible, I heard it in my mind, “I consumed the sacrifice.” I was in awe. I realized that God would only use my vocal cords to speak to His people if I was willing for Him to do so.