“Keep yourselves in the love of God”
Jude 20-25 But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost, 21Keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life. 22And of some have compassion, making a difference: 23And others save with fear, pulling them out of the fire; hating even the garment spotted by the flesh. 24Now unto Him that is able to keep you from falling, and to present you faultless before the presence of His glory with exceeding joy, 25To the only wise God our Saviour, be glory and majesty, dominion and power, both now and ever. Amen.
Why does Jude; the half brother of Jesus; say this? Praying in the Holy Ghost is an act of faith, Faith in what?
I Corinthians 14:21-22 In the law it is written, (Isaiah 28:11)With men of other tongues and other lips will I speak unto this people; and yet for all that will they not hear me, saith the Lord. Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.
Isaiah 28:9-13 9Whom shall he teach knowledge? and whom shall he make to understand doctrine? them that are weaned from the milk, and drawn from the breasts.  10For precept must be upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little:  11For with stammering lips and another tongue will he speak to this people.   12To whom he said, This is the rest wherewith ye may cause the weary to rest; and this is the refreshing: yet they would not hear. 13But the word of the LORD was unto them precept upon precept, precept upon precept; line upon line, line upon line; here a little, and there a little; that they might go, and fall backward, and be broken, and snared, and taken.
Tongues and the intercession of the Holy Ghost through your most Holy Faith praying in the Holy Ghost, Hebrews 11:6 Without faith we are unable to please Him.
Ephesians 6:18 Praying always with all prayer and supplication in the Spirit, (tongues) and watching thereunto with all perseverance and supplication for all saints;
Why pray in tongues, in the Spirit, Romans 8:26-28  Likewise the Spirit also helps our infirmities: for we know not what we should pray for as we ought: but the Spirit itself makes intercession for us with groanings which cannot be uttered. 27And he that searches the hearts knows what is the mind of the Spirit, because He makes intercession for the saints according to the will of God.  28And we know that all things work together for good to them that love God, to them who are the called according to His purpose.
Are you the called according to His purpose? You are if you just got done praying in tongues by your most Holy faith. Yes faith is an act of trust in God to do a perfect work, our rest in knowing that a perfect thing is going to happen according to His will not ours. The New Covenant:
Hebrews 10:14-17 For by one offering He hath perfected for ever them that are sanctified. 15Whereof the Holy Ghost also is a witness to us: for after that he had said before, 16This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them; 17And their sins and iniquities will I remember no more.
Father forever we who are sanctified, Halle lu YAH, praying in faith and in the Holy Ghost.