Many Pentecostal churches assert that speaking in tongues is the initial evidence of the baptism of the Holy Spirit. I don't believe this to be true. In the words of my brother Jason, the error is that they "conflate the manifestations [gifts] of the Spirit with the fruit of the Spirit." The fruit of the Spirit is the evidence that the Spirit is alive in a believer. The gifts of the Spirit are given to the body for the "common good" (1 Corinthians 12:7). Each gift plays a particular role within the body as well as for the unbelievers. For example, the gift of healing is given to the body because God desires for us to be made whole spiritually as well as physically. When the unbeliever witnesses or experiences supernatural healing, it produces faith that leads to salvation. Jesus would often heal people as part of His earthly ministry, but when people from his hometown started seeking healing without glorifying God, He stopped.
Just as the gift of healing has its purpose inside and outside the church, so does speaking in tongues. The gift of tongues is meant to be used as a personal prayer language for talking with God or as a supernatural ability to speak the right words (or even the right language) when confronted with an opportunity to proclaim the gospel. In the context of a church service, tongues are not meant to be used corporately unless there is an interpretation. When unbelievers hear someone speaking in tongues, they curiously wonder at the supernatural utterances. The gift of tongues is an unmistakenly supernatural occurrence, so even within the body, it is natural to conclude that a person is filled with the Spirit if they are speaking in tongues. However, I do not believe that the logical inversion of this statement is true: that if a person does not speak in tongues, they are not filled with the Spirit.
Jesus said that a "tree is known by its own fruit" (Luke 6:44). The fruit of the Spirit is the evidence that we are filled with the Spirit and abiding in the vine. In the middle of his encouragement to the Corinthian church to seek the gifts of the Holy Spirit, Paul had to remind them that exhibiting the fruit of the Spirit was more important than any of the gifts (1 Corinthians 12-14). I have often wondered why I have seen many non-Pentecostal Christians exhibiting the fruit of the Spirit and many Pentecostal Christians who are representing Christ poorly. Perhaps it is because Pentecostal believers tend to seek the gifts of the Spirit rather than seeking to exhibit the fruit of the Spirit.
Practically speaking, we should still seek the gifts of the Holy Spirit because they are promises from God to bless us. Wouldn't it be awesome if the Spirit could give you exactly the right words to say when talking with your Heavenly Father? He does! All we need to do is ask for the gift expectantly and persistently.
There are several questions surrounding this topic that I still don't have answers to. Some of my friends who may read this post will claim that speaking in tongues is the initial evidence of the baptism of the Holy Spirit, while others don't believe that the gifts of the Spirit exist at all anymore. Whatever your views on this topic are, I'd love to discuss this more with you!