Saint Chrysostom says, "Discernment of spirits is knowledge of who is spiritual, that is, filled with the Holy Spirit, and who is not spiritual, but speaks only from himself. It is knowledge of who is a prophet and who is a deceiver.
At that time there was great danger from false prophets, because the devil tried in every way to set falsehood against truth."
What are kinds of tongues? This is the gift of speaking in various languages, not by learning them, but by a gift from the Spirit of God.
The Roman Empire was filled with peoples of many languages. So that no one would be deprived of the possibility of hearing the good tidings, the gift of speaking different languages was given everywhere.
This gift and the gift of the word of wisdom were the most necessary.
"The Apostle gave this gift the last place, and the gift of teaching the first, because for the sake of both these gifts all the others were given, so that the preaching might be received with faith" (Theodoret).
"This gift of tongues was considered great. The Apostles received it first of all, and many of the Corinthians had it. But the gift of teaching is higher.
The Apostle placed it first, and speaks of this one at the end. For this gift exists for the sake of that one, as do all the rest, prophecies, operations of powers, and gifts of healings.
Nothing can equal it, as he himself says: 'Let the presbyters who rule well be counted worthy of double honor, especially those who labor in word and teaching' (1 Tim 5:17)" (Saint Chrysostom).
What is the interpretation of tongues? It is the gift of interpreting for others what has been said in foreign languages.
"One man himself knew what he was saying, but could not interpret it to another. Another had the capacity for both" (Saint Chrysostom).
"This too was a spiritual gift. Often a man who knew only the Hellenic language would translate for the hearers when another spoke in the Scythian or Thracian tongue" (Theodoret).
"Those who spoke in tongues sometimes had this gift themselves and interpreted themselves" (Oecumenius).
In enumerating such gifts, the Apostle explains that they are given "by the same Spirit" and "through the same Spirit." He teaches that although the streams are diverse, the source is certainly one.
But Theodoret says he judged even this insufficient and added: Verse 11, "But one and the same Spirit works all these things, distributing to each one by authority as He wills."