There is a story of a young country boy who found himself in the possession of some tree seeds. He did not know what kind of tree these seeds might produce, but he planted the seeds in some very fertile soil.
As the years passed the boy watched with interest as the young sapling would grow and grow. With his limited resources, he could not identify what kind of tree it was either by the leaves or the bark. In his teenage years, his buddies and he would take guesses and place friendly bets on what sort of tree was growing.
When he was a young man, packing up to leave the country, he made one last trip to the field - to this tree - and there upon its branches was a mature, bright, shiny red apple.
He now knew what kind of tree had been growing there all these years. He knew the tree by its fruit.
How can we tell whether or not the Holy Spirit of God has been planted inside of us? How can we look in the proverbial mirror and have proof positive that we are maturing and growing more and more into the image of Jesus, which is the ministry of the Holy Spirit?
We can know by looking at the fruit.