Acts chapter 2 records a great change which happened when God first made being born of His spirit available to humanity. Scripture tells that previously, spirit was conditionally placed upon individuals in portions for certain reasons or purposes - and it could be removed / lost. But now when it is born within it cannot be lost or removed!
To mark such a great occasion, on Pentecost God used a symbolic vision of flames parted over each person to signify the imparting of this spirit. This great phenomena was outward indication of inner spiritual change.
God giving this new spiritual nature to those who claim it is ‘life-giving’. The recipient's decision to change their lifestyles to align with this spiritual nature, makes the gift ‘life-changing’...
Just as we know that we have natural life by demonstrating physical abilities. Similarly, the way we know that we have received God’s spiritual life today is not by hoping to see 'flaming phenomena' of the first outpouring... But, by simply demonstrating the abilities which Scripture says evidence this new form of life. [See: 1 Cor. chp. 12-14]
“So that if any one has received the same spirit of Christ, they become a new creature: the old state of things has passed away; a new state of things has come into existence.” [2 Cor. 5:17]
“Cease copying the behavior and customs of this world, but let God transform you into a new person by changing the way you think. Then you will learn by testing it for yourself that the will of God is always good and acceptable and perfect.” [Rom 12:2]
Maybe we didn’t receive a handbook on the many changes that happen during our natural lives… But Scripture is complete with instructions about the great, beneficial change which Gods spiritual life offers those who claim it!
Transformation of our thinking is the best Sign of spiritual Change in our lives!