Jeremiah 17:9-10 — The heart is deceitful above all things, and desperately wicked: who can know it? I the Lord search the heart, I try the reins, even to give every man according to his ways, and according to the fruit of his doings.
My lovely Myra is often surprised by wickedness. Somehow I’m more realistic, or experienced or cynical and so not often surprised, but Myra is often surprised by wickedness in the wide world, and by the petty malice of those close to her. The truth is though, I’m not really as smart as I think I am, and sometimes I get blindsided, and this morning’s devotion reminded me that there is only one who really knows what anyone is capable of.
We were reading John 2. It finishes:

Now when he was in Jerusalem at the passover, in the feast day, many believed in his name, when they saw the miracles which he did. But Jesus did not commit himself unto them, because he knew all men, and needed not that any should testify of man; for he knew what was in man. (John 2:23-25)
All those people, easily swayed, “believed” in Jesus, because of the signs He did. He, however did not “commit” Himself to them. The Greek is interesting. The word used for “believed”, and the word used for “commit” are different forms of the same word which has, at its heart, the idea of trusting in or placing faith in. Jesus would not reciprocate the “trust” of the crowds because He knew how unreliable it would prove to be. 
Jesus was there before the beginning of time, when we were imagined. He was there before we were born, when we were conceived and grew in our mother’s wombs. He was there when each of us was born, slaves to sin. He was there when we were saved. He is with us now, watching us fall short of His glory minute by minute, day by day.

The Lord spoke through Jeremiah and made it clear that no one of us can know what is in the heart of any other. In fact we cannot even know our own hearts. He, on the other hand, knows and studies each one of us. The end of that study is that each of us, in the end, will receive the due reward for who we are and what we have done.

Having considered all this, what are we to do? We are to love our neighbors as ourselves! We are to be wise as serpents — never surprised at human failings, and gentle as doves — leaving it to God to reward and punish.