1. Speaking in Tongues is a command.

And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues; They shall take up serpents; and if they drink any deadly thing, it shall not hurt them; they shall lay hands on the sick, and they shall recover. (Mark 16: 17-18).

 2. Speaking in Tongues is necessary for Spiritual strength.

These be they who separate themselves, sensual, having not the Spirit. But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost, Keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life. (Jude 19-21).

3. Speaking in Tongues is the precursor for the power needed to effectively accomplish the Great Commandment.

But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. (Acts 1:8).

4. Speaking in Tongues is the initial sign of having been Filled With or Baptized In the Holy Spirit.

And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance. (Acts 2:4)

5. Speaking in Tongues is the gateway or bridge over into operating (co-laboring) with the Holy Spirit in the Supernatural Gifts of the Spirit.

And they went forth, and preached every where, the Lord working with them, and confirming the word with signs following. Amen. (Mark 16:20).

6. Speaking in Tongues is speaking directly to the Lord.

For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries. (1 Corinthians 14:2)

7. Revelation is revealed to the spirit when one speaks in the Spirit. In the following scriptural passage Paul is asking the Saints of Ephesus to pray in the Spirit for him that he might receive Utterance (tongues) relating to the revelation of the mystery of the Gospel.

Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints; And for me, that utterance may be given unto me, that I may open my mouth boldly, to make known the mystery of the gospel, For which I am an ambassador in bonds: that therein I may speak boldly, as I ought to speak. (Ephesians 6:18-20).

8. Saints often are able to share words of edification, exhortation and comfort to someone whose language they don’t speak nor does that person speak the Saint’s language — doing so by the Holy Spirit in Tongues.

And there were dwelling at Jerusalem Jews, devout men, out of every nation under heaven. Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language. (Acts 2:5-6).

9. Praying in Tongues is essential when we don’t know what to pray for. This is likely the single most important reason to pray in the Spirit.

Likewise the Spirit also helpeth our infirmities: for we know not what we should pray for as we ought: but the Spirit itself maketh intercession for us with groanings which cannot be uttered. (Romans 8:26).

10. Praying in the Spirit is an essential weapon of spiritual warfare. The following scriptural passage calls the Sword of the Spirit the Rhema Word of God which carries all the Power and Might of the Godhead. This Power flows from Heaven and through our mouths when we Pray in Tongues.

And take the helmet of salvation, and the sword of the Spirit, which is the word of God: Praying always with all prayer and supplication in the Spirit, and watching thereunto with all perseverance and supplication for all saints; (Ephesians 6: 17-18).