The fruits and effects He produces

(J. C. Ryle, "The Holy Spirit")

"When He comes, He will convict the world about
 sin, righteousness, and judgment." (John 16:8)

Where the Holy Spirit is, there will always be deep
conviction of sin--and true repentance for it. It is
His special office to convince of sin.

He shows the exceeding holiness of God.

He teaches the exceeding corruption and
infirmity of our nature.

He strips us of our blind self-righteousness.

He opens our eyes to our awful guilt, folly and danger.

He fills the heart with sorrow, contrition, and abhorrence
for sin--as the abominable thing which God hates.

He who knows nothing of all this, and saunters
carelessly through life, thoughtless about sin, and
indifferent and unconcerned about his soul, is a
dead man before God! He has not the Holy Spirit.

The presence of the Holy Spirit in a man's heart can
only be known by the fruits and effects He produces.
Mysterious and invisible to mortal eye as His operations
are, they always lead to certain visible and tangible results.

Just as you know there is life in a tree by its sap, buds,
leaves and fruits--just so you may know the Spirit to be
in a man's heart by the influence He exercises over his
thoughts, affections, opinions, habits, and life. I lay this
down broadly and unhesitatingly. I see it clearly marked
out in our Lord Jesus Christ's words, "Every tree is known
by his own fruit." (Luke 6:44)