The Enemy Never Sleeps

Here is another story Jesus told: "The Kingdom of Heaven is like a
  farmer who planted good seed in his field. But that night as
  everyone slept, his enemy came and planted weeds among the wheat.
  When the crop began to grow and produce grain, the weeds also grew.
  The farmer's servants came and told him, 'Sir, the field where you
  planted that good seed is full of weeds!' "'An enemy has done it!'
  the farmer exclaimed. "'Shall we pull out the weeds?' they asked.
  "He replied, 'No, you'll hurt the wheat if you do. Let both grow
  together until the harvest. Then I will tell the harvesters to sort
  out the weeds and burn them and to put the wheat in the barn.'" (Mat
  13:24-30 NLT)