Why is salvation by faith?

(Thomas Watson, "Body of Divinity")

"For it is by grace you have been saved, through
 faith—and this not from yourselves, it is the gift
 of God—not by works, so that no one can boast." 
    Ephesians 2:8-9 

"Jesus said to the woman—Your faith has saved
 you; go in peace." Luke 7:50

Why is salvation by faith? 

To exclude all glorying in the creature. Faith is a 
humble grace. If salvation were by repentance or 
works, a man would say, "It is my righteousness 
which has saved me!" But if it is of faith, where is 
boasting? Faith fetches all from Christ—and gives
all the glory to Christ! 

God's believing people are a humble people.  
"Be clothed with humility." God's people shrink into 
nothing in their own thoughts. David cries out, "I am 
a worm, and not a man!" Though a saint, though a 
king—yet a worm! When Moses' face shined, he 
covered it with a veil. When God's people shine most 
in grace—they are covered with the veil of humility. 
Abraham the father of the faithful, confesses, "I am
nothing but dust and ashes." "God resists the proud."
Surely, God will not take to be with Himself in glory,
such as whom He resists.

God's believing people are a willing people. 
Though they cannot serve God perfectly—they serve 
Him willingly. They do not grudge God a little time 
spent in His worship. They do not murmur at sufferings. 
They will go through a sea and a wilderness—if God calls. 
"Your people shall be a willing people." This spontaneity 
and willingness is from the attractive power of God's 
Spirit. The Spirit does not force—but sweetly draws the 
will. This willingness makes all our services acceptable. 
God sometimes accepts of willingness without the 
work—but never the work without willingness.

God's believing people are a consecrated people. 
They have "holiness to the Lord" written upon them. 
"You are a holy people to the Lord your God." God's 
people are separated from the world—and sanctified 
by the Spirit. The priests under the law were not only 
to wash in the laver—but were arrayed with glorious 
apparel. This was typical, to show that God's people 
are not only washed from gross sins—but adorned 
with holiness of life. They bear not only God's name
—but His image! Holiness is God's stamp; if He does 
not see this stamp upon us, He will not own us for 
His believing people.

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