THE IMPORTANCE OF THE HOLY SPIRIT
The Holy Spirit is the most important gift a Christian has ever received. One of the important benefits that come to a Christian when he receives the Holy Spirit is the ability to speak in other tongues. We speak in tongues for the following important reasons and benefits:
TO BUILD UP OUR FAITH (JUDE 20)
As we speak in other tongues we build up our faith. Each believer has been given a measure of faith. This measure can be improved upon through prayers. Speaking in other tongues is an effective way of praying to God because at that time it is your spirit that prays (1 Cor 14:14). Boldness comes to your spirit as you speak in other tongues.
TO GLORIFY GOD (Acts 10:46)
There is a greater depth at which you will worship God when you have the infilling of the Holy Spirit and can worship Him in other tongues. Your mind is no more at work here but you worship Him in spirit and in truth (John 4:23). God is a Spirit and we must relate to Him that way.
TO SPEAK MYSTERIES TO GOD (1 Cor 14:2)
Because of the unfruitfulness of the mind (1 Cor 14:14) you speak secret truths and hidden things not obvious to the understanding yet. This means you speak mysteries unto God. This leads you to receiving divine revelations as you speak them.
IT’S A SIGN OF THE BELIEVER (Mark 16:17)
Jesus said it emphatically that speaking in tongues is a sign of knowing those who have believed.
THE DIFFERENCCE BETWEEN MARK 16:17 AND 1 CORINTHIANS 12:10
In mark 16:17 the signs of the believer is seen and speaking in tongues is a sign that must follow all who believe while in 1 Corinthians 12:10, we see the gifts of the Holy Spirit enumerated. The Holy Spirit to each individual distributes these gifts as He wills (1 Cor. 12:11). These gifts are distributed differently to every individual according to God’s own will (Hebrews 2:4).
Thus the tongues in Mark are a sign for all believers while those in 1 Corinthians are gifts which may not necessarily manifest in every Christian.