A very delicate thing

(Arthur Pink, "The Eye of Faith")

Faith is frequently represented in Scripture, under the metaphor of bodily sight. Of Moses it is said that "he endured as seeing Him who is invisible" Hebrews 11:27. That is, his heart was sustained through faith's being occupied with the mighty God.

The eye is a very delicate thing—it is soon hurt and easily damaged. A tiny speck of dust will cause pain and make it weep. It is very striking to note, that this is the very way to recovery—it weeps out the dust that gets into it. 

Just so, faith is a most delicate grace, thriving best in a pure conscience. Hence the apostle speaks of "holding the mystery of the faith in a pure conscience" (1 Timothy 3:9). The lively actings of faith are soon marred by the dust of sin, or by the vanities of the world getting into the heart where it is seated. And wherever true faith is—if it is hurt by sin—it vents itself in a way of godly sorrow.