Job begins by pointing out the lack of sympathy on the part of his friends. Job 21:2-6 reads:
"Listen carefully to my speech, and let this be your consolation. Bear with me that I may speak, and after I have spoken, keep mocking. As for me, is my complaint against man? And if it were, why should I not be impatient? Look at me and be astonished; put your hand over your mouth. Even when I remember I am terrified, and trembling takes hold of my flesh."
Although Job has plenty of complaints against his friends, he really wants to talk with God.
Job believes that suffering is not necessarily proof of personal sin any more than the lack of suffering is proof of righteousness. He begins proving this by speaking of the prosperity of the wicked.
"Why do the wicked live and become old, yes, become mighty in power? Their descendants are established with them in their sight, and their offspring before their eyes. Their houses are safe from fear, neither is the rod of God upon them. Their bull breeds without failure; their cow calves without miscarriage. They send forth their little ones like a flock, and their children dance. They sing to the tambourine and harp, and rejoice to the sound of the flute. They spend their days in wealth, and in a moment go down to the grave [in other words, without prolonged suffering, -SRB]. Yet they say to God, 'Depart from us, for we do not desire the knowledge of Your ways. Who is the Almighty that we should serve Him? And what profit do we have if we pray to Him?' Indeed their prosperity is not in their hand; the counsel of the wicked is far from me" (Job 21:7-16 cf. Exo. 5:2).
Many wicked men are blessed richly--by the providence of God--despite their rejection of Him! However, Job realizes that bad things also befall evil men (cf. Job 21:17,18). Since this is the case (and can be proved via observation), Job has established his point. Suffering does not inherently prove that one is unrighteous.
Job's opponents have actually been questioning the Lord's wisdom by suggesting a theory of God's activity that does not correspond with the observable facts! Job rebukes his friends by asking - "Can anyone teach God knowledge, since He judges those on high?" (Job 21:22). Job believes that God knows what He is doing, but the belief of his friends questions God's wisdom since it does not correspond with reality. No generalizations can accurately be made regarding the temporal punishment of the wicked. Some die miserably and some die in prosperity, but all die (cf. Job 21:23-26)! One's earthly circumstances cannot be used as a barometer for determining his spiritual condition.
Job then speaks of the wicked man's end - "For the wicked are reserved for the day of doom; they shall be brought out on the day of wrath" (Job 21:30). As Job concludes he asks - "How then can you comfort me with empty words, since falsehood remains in your answers?" (21:34). Job has given up any expectation of his friends comforting him since their ideas about God and punishment are false. They simply don't understand.