One way to study the Bible is by marking the keywords of a book. Take a keyword and follow it through to see how it is used in the text. In the book of Job, "know" is such a word. It is used often, 87 times, in fact. However, what is most interesting in the book is how it is used.
When tragedy strikes, a conversation begins between Job and his friends in which what they "know" (or think they know) is very much at the forefront. Job will argue that he doesn't know why this is happening because he has done no wrong. His three friends contend that they know Job must have committed some great sin. All the evidence they think they need to see is in Job's circumstances.
Job answers that indeed he does not know what he has done. Still, he does know one crucial fact; that God is in control (see 19:25; 31:6, et al.).
After several rounds, a fourth friend (Elihu) stands up. He has heard enough. He rebukes these four old men for running their mouths and not doing what is right (32:6-7). This young man just knows he has it all figured out (32:10, 17; 33:3; 36:4, et al.).
Then God speaks. Rather than answer Job or his friends, God challenges them. If they know so much, let them give some knowledge to the Lord God (38:2-5, 12, 18, 21, 33; 39:1-2; 40:6). In 40:1-6, Job answers the Lord. He says, "I know nothing but You. You teach me."
So, from the book of Job, what can we know?
That we do not know why any particular person is suffering.
That we can make the suffering worse for someone when we presume to know.
That the only thing we need to know when it comes to suffering is the One in control.
I may not know what tomorrow may bring. I may never know why I endure certain things. All I need to know is the Lord God. He knows all, is all-powerful, and cares for each of us.