The Hebrew word translated here as "cruel" is 'azkar, and in this case, it is better rendered "fierce." If we read Job 30 in its entirety, we will see that verse 21 is among those often applied in a dual, prophetic sense to the last hours of Jesus' human life. In another dual prophecy, Isaiah 53:10, we learn that it actually pleased God to bruise His own beloved Son, to put Him to grief, and even to make Him the ultimate sin offering!
It begins to become clear that God's standards of cruelty, fierceness, and even pleasure are not the same as man's. In a similar way as the Father's "fierceness" concerning Jesus' trials was necessary for the salvation of mankind, Job's afflictions were likewise necessary for his own ultimate benefit, as we find out later in Job's account (see Job 42:1-6).
What about us? Do we ever feel that God is cruel or fierce toward us? For example, when we do not get what we want just when we want it? Or when we or a loved one are not healed right away? Or when a loved one dies? Do we cry out, "My God, why have you forsaken me?" (Psalm 22:1).
Neither God the Father nor the Lord Jesus Christ is inherently cruel. On the contrary, they are endlessly loving, longsuffering, patient, and merciful. They have solemnly and repeatedly promised never to leave us nor forsake us (Deuteronomy 31:6; Joshua 1:5; Hebrews 13:5).
Cruelty is assuredly not part of God's "way of give." It is, however, part of Satan's "way of get," which he has foisted on mankind for six thousand years. Satan is the wicked one (Matthew 13:19, 38; I John 2:13-14; 3:12; 5:18). He is the chief adversary against God and His children (I Peter 5:8). He is the chief of our wicked, unrighteous, lying enemies; and as such, he is the instigator of all the cruelty that our enemies commit against us.
Don't Be Cruel!
Job 30:18-25 adds more complaints that essentially claim, "If I, Job, can see these problems, why can't God? And yet He does nothing!" His mindset is such now that he is blaming God for everything that goes wrong in his life. The sum of these charges is that God is guilty while Job is an innocent victim of God's blind, uncaring negligence.
John W. Ritenbaugh
Job, Self-Righteousness, and Humility