“…the love of God is shed abroad in our hearts by the Holy Ghost which is given unto us” (Romans 5:5).
When the Lord Jesus Christ told His disciples that He would be leaving them shortly to lay down His life they were sad. They might have said to Him, “Lord, for Your sake we left our homes and business. Now if You leave us we will be forsaken, like orphans”. But the Lord answered them, “I will not leave you comfortless”, or “orphans” as in the margin of the Authorised Version (John 14:18). The Holy Spirit, as Comforter, pours God’s love into us. When we are lonely and unloved we can taste this love and protective care, and the feeling of being orphans is gone. So there is no need for us to say, “I have no father or mother, or brother or sister to look after me. I have no home to go to”. Those who have a home may say, “I can go home to my parents when I am ill or in need and they will look after me”. But God has promised not to leave us but has sent us the Comforter Who will bring His love into us in fulness (Rom. 5:5).
The Holy Spirit brings divine love into us to comfort us, and the same love gives us a burden for perishing souls and a loving concern for the backslidden, and the sick and suffering. On hearing of someone’s troubles or sickness our hearts reach out to them in love and sympathy, and we desire to comfort them by writing to them, visiting them and by praying for them. We do these things not as a matter of formality but because the love of God constraints us (Rom. 12:15). The privilege of being comforted and of comforting others by the comfort wherewith we ourselves are comforted of God is proof of a spiritual believer.
Also the Holy Spirit helps us to understand the truth and opens our eyes to see great and hidden mysteries of God’s Word. There are many believers who know little or nothing of Science., History, Geography, Philosophy or Botany, but they do understand and enjoy God’s Word, because the Holy Spirit of Truth reveals things to them which are hidden from the wise and the prudent (Matt. 11:25, Luke 10:21). Carnal Christians enjoy singing hymns and lyrics and prefer to hear moral sermons, but when the deeper things are shown from God’s Word they fall asleep. It is not because they are tired but just because they can neither understand them nor are they interested in such spiritual things. But a spiritual believer is eager to learn everything the Holy Spirit will teach him, and is hungry for more and more God’s Word, and can understand and enjoy the hidden mysteries of God. This hunger for, and the ability to understand the truth of God’s Word, is also a proof that a believer is becoming spiritually mature.