I have said all these things to you to keep you from falling away. They will put you out of the synagogues. Indeed, the hour is coming when whoever kills you will think he is offering service to God. And they will do these things because they have not known the Father, nor me. But I have said these things to you, that when their hour comes you may remember that I told them to you. "I did not say these things to you from the beginning, because I was with you.
Religion can be a dangerous thing. Under the influence of religious fervor Saul of Tarsus (before he became Paul) chased down and imprisoned Jews for believing in Jesus. In modern times misguided Muslims bomb and murder innocent victims in the name of God. These things all happen mainly because those religious people do not know God. For if they knew God they would have acted in ways commensurate with the character of God.
This idea that religious people would do such things is so ludicrous that Jesus had to warn his disciples beforehand so that they would be prepared when persecution by religious people commenced. Who could have imagined that Jews who are commanded to love God and their neighbors would have acted in such a hateful way. These who were supposedly God's people would act in such a way that revealed that they did not know God at all.
I love you Lord. Help me to know you better and reflect your character in my life.