After God has asked Job’s questions regarding the nature and animals, God told Job to answer Him (40:1). Job started to realize about his insignificant and was not able to answer God (40:4-5). However Job is not at the level of understanding of himself and of God where God wanted him to be. So God selected two animals out of all His creations to continue to show His majesty.
The reason why God asked Job questions about His creations was because Job was willing to condemn God by accusing God for being injustice to defense and justify himself (v8). God wanted to show Job that He is the creator of all things, His wisdom and power is infinitely higher than Job. God has the authority to govern His creations according to His perfect good will.
Since Job thought he was more righteous than God, God told Job why don’t he cloth himself with honor and majesty and judge the world by humbling the proud (40:12), by punishing the wicked (40:12)? In another words, God was telling Job: “Why don’t you try to be Me and do My job, and see if you have the wisdom and power to do the job (40:10-13). If Job could do that, God would confess Job’s own right hand could save himself (40:14).
God used two powerful and fearful creatures to challenge Job. The one in chapter 40 is called Behemoth, and the one is chapter 41 is called Leviathan (Job 3:8; Ps 74:14; 104:26; Is 27:1). Some people suggested Behemoth is referring to hippopotamus, and Leviathan is referring to crocodiles. However hippos have short tail, the Behemoth described in chapter 40 has a tail like cedar (40:17). As for Leviathan, the descriptions do not completely match a crocodile neither. 41:18-21 seems to suggest that this creature could breath fire out of its mouth!
These two creatures could possibly referring to dinosaurs.
God challenged Job to capture a Behemoth (v24)? How about could he subdue a Leviathan (41:1)? If Job could not conquer these creatures, on what basis he stood to challenge the Creator (41:10)?
Have you ever questioned or accused God so that we ourselves could be justified? If we could spend time to observe God’s creations, we will surely marvel at His wisdom and power, which is infinitely higher than ours. We have not given anything to God, because whatever is under the whole heaven belongs to God (41:11-12). Thus everything God has given to us are given by His grace. God knows what He is doing. Our job is to trust in Him.