It must be stated at the outset, that there is no statement in the New Testament that speaking in tongues is the initial evidence of the Holy Spirit’s infilling.
This claim is similar to many other statements Christians frequently make, e.g., “the Trinity” is a term unknown to the New Testament writers and a doctrine that was not taught until at least a century after their passing and yet is spoken of as if that is settled truth. We receive it by faith.
This should remind us that we all should stick to the original deposit of the apostles as sound doctrine and not be too prescriptive in our efforts to explain truth. Let’s try to get things in context, in balance, rather than trying to defend our “position” whatever that may be. Still, listening to one another with respect and gentle discussion can be helpful.
Now in Acts, there are 5 accounts of people receiving the Holy Spirit and 3 out of the 5 mention speaking in tongues as a consequence. Of course this absence of speaking in tongues in 2 of the 5 cases does not prove anything, one way or the other. It just proves that Luke only mentions speaking in tongues 3 times.
Paul writing to the Corinthians alludes to the rule in Deuteronomy that facts are established “out of the mouths of 2 or 3 witnesses”. Now we have not just 2 but 3 instances of tongues following the coming of the Holy Spirit!
Yet Paul claimed to speak in tongues more than anybody and wished all the Corinthian believers did so also. We can also ask why did the apostles pray for the Samaritan believers to receive the Holy Spirit (Acts 8)—what did they expect to see? How did they know they had received the Holy Spirit? We are not told, though we might make a deduction.
And how did Peter know that the people assembled in the house of Cornelius (Acts 10) had received the Spirit? Peter was so certain they had received “just as we had at the beginning” that he could not deny them baptism.
These are good questions and we may be tempted to answer them with a doctrine, very tempted! But take care, that we are not preaching and teaching beyond what the apostles taught.
But there are other results following the “clothing” of the Holy Spirit upon the original believers. We read of great anointing, extraordinary boldness, confident testimony, signs and wonders performed, the Kingdom of God shown in power and not just talk, and so on. Some prophesied, others praised God and there was great awe, a holy fear of God, great generosity and hospitality, sharing of resources, and above all, love for one another.
Yes love! Paul in 1 Corinthians 13 firmly tells his hearers that speaking in tongues (and other miraculous signs) are useless if the user does not act in love! And Jesus said that knowing him is the priority rather than our works (Matthew 7). So there is a bit more to this question!
If people are “filled with the Holy Spirit” we ought to expect the fruit of the Spirit to be wonderfully manifested along with power and authority, boldness and signs. It is clear that the Lord Jesus acted with great compassion when he healed people and set them free. Without love, Paul said “I am nothing”. If the only sign of a claimed experience of the Holy Spirit is speaking in tongues, with an absence of other signs and the fruit of the Spirit in our lives, then we might be just a “resounding gong or a clanging cymbal”.
We are on more solid ground when we read 1 Corinthians 14. There Paul talks frankly about the great value of speaking in tongues, not only for himself but for all. Yet he is even more encouraging for believers to prophesy when they come together.
We must respect the views of one another as we debate things and let love be genuine. We must maintain the unity of the Spirit in the bonds of peace and remember that only in Jesus do we have “the way, the truth and the life”. Though others may be helpful, finally we sit only at his feet.