How shall we know if we have saving faith?

(Thomas Watson, "Body of Divinity")

How shall we know if we have saving faith?

By the noble fruits and effects of saving faith.

True faith is a Christ-prizing grace—it puts a high
valuation upon Christ. "To you who believe—He is
precious." See how Paul styles all things in comparison
with Christ, "I count all things but rubbish, that I may
win Christ." Do we set a high estimate upon Christ?
Could we be willing to part with the wedge of gold
—for the Pearl of great price?

True faith is a refining grace. Faith is in the soul as
fire among metals—it refines and purifies. Morality
may wash the outside—but faith washes the inside.
"Having purified their hearts by faith." Faith makes
the heart a holy of holies. Faith is a virgin-grace;
though it does not take away the life of sin—yet it
takes away the love of sin. Examine if your hearts
are an unclean fountain, sending out the mud and
mire of pride and envy. If there are legions of lusts
in your soul, there is no faith. Faith is a heavenly
plant, which will not grow in an impure soil.

True faith is an obediential grace. "The obedience
of faith." Faith melts our will into God's. It runs at God's
call. If God commands duty (though cross to flesh and
blood) faith obeys. "By faith Abraham obeyed." Faith is
not an idle grace. As it has an eye to see Christ—so it
has a hand to work for Him. It not only believes God's
promises—but obeys His commands. It is not having
knowledge that will evidence you to be believers; the
devil has knowledge, but lacks obedience—and that
makes him a devil. The true obedience of faith, is a
cheerful obedience. God's commands do not seem
grievous. Have you obedience, and obey cheerfully?
Do you look upon God's command as your burden—
or privilege; as an iron fetter about your leg—or as
a gold chain about your neck?

True faith is an assimilating grace. It changes the
soul into the image of the object; it makes it like Christ.
Never did any look upon Christ with a believing eye—but
he was made like Christ. A deformed person may look on
a beautiful object, and not be made beautiful; but faith
looking on Christ—transforms a man, and turns him into
His similitude.

Looking on a bleeding Christ—causes a soft bleeding heart.

Looking on a holy Christ—causes sanctity of heart.

Looking on a humble Christ—makes the heart humble.

As the chameleon is changed into the color of that
which it looks upon—so faith, looking on Christ,
changes the Christian into the similitude of Christ.

True faith grows. All living things grow. Growth of faith
is seen by doing duties in a more spiritual manner, with
more fervency. When an apple has done growing in
bigness, it grows in sweetness. Just so, duties performed
in love and are sweeter, and come off with a better relish.