If I wash myself with snow water - If I should make myself as pure as possible, and should become, in my view, perfectly holy. Snow water, it seems, was regarded as especially pure. The whiteness of snow itself perhaps suggested the idea that the water of melted snow was better than other for purification. Washing the hands formerly was an emblem of cleansing from guilt. Hence Pilate, when he gave up the Savior to death, took water and washed his hands before the multitude, and said that he was innocent of his blood; Matthew 27:24. The expression used here by Job, also is imitated by the Psalmist, to denote his innocence:

I will wash mine hands in innocency:

So will I compass thine altar, O Lord. Psalm 26:6.

Verily I have cleansed my heart in vain,

And washed my hands in innocency.

Job 9:30 Parallel Commentaries

The Power of God
The next attribute is God's power. Job 9:19. If I speak of strength, lo, he is strong.' In this chapter is a magnificent description of God's power. Lo, he is strong.' The Hebrew word for strong signifies a conquering, prevailing strength. He is strong.' The superlative degree is intended here; viz., He is most strong. He is called El-shaddai, God almighty. Gen 17:7. His almightiness lies in this, that he can do whatever is feasible. Divines distinguish between authority and power. God has both. …
Thomas Watson—A Body of Divinity

Whether Man Can Know that He Has Grace?
Objection 1: It would seem that man can know that he has grace. For grace by its physical reality is in the soul. Now the soul has most certain knowledge of those things that are in it by their physical reality, as appears from Augustine (Gen. ad lit. xii, 31). Hence grace may be known most certainly by one who has grace. Objection 2: Further, as knowledge is a gift of God, so is grace. But whoever receives knowledge from God, knows that he has knowledge, according to Wis. 7:17: The Lord "hath given …
Saint Thomas Aquinas—Summa Theologica

Opposition to Messiah in Vain
He that sitteth in the heavens shall laugh; the Lord shall have them in derision. T he extent and efficacy [effects] of the depravity of mankind cannot be fully estimated by the conduct of heathens destitute of divine revelation. We may say of the Gospel, in one sense, what the Apostle says of the Law, It entered that sin might abound (Romans 5:20) . It afforded occasion for displaying the alienation of the heart of man from the blessed God, in the strongest light. The sensuality, oppression and …
John Newton—Messiah Vol. 2