These two series of scriptures came to mind when I read your question. I'm sure there may be other observations as well.
Matthew 13:24-30
24 Another parable put he forth unto them, saying, The kingdom of heaven is likened unto a man which sowed good seed in his field:
25 But while men slept, his enemy came and sowed tares among the wheat, and went his way.
26 But when the blade was sprung up, and brought forth fruit, then appeared the tares also.
27 So the servants of the householder came and said unto him, Sir, didst not thou sow good seed in thy field? from whence then hath it tares?
28 He said unto them, An enemy hath done this. The servants said unto him, Wilt thou then that we go and gather them up?
29 But he said, Nay; lest while ye gather up the tares, ye root up also the wheat with them.
30 Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.
Judges 2:20-23
20 And the anger of the LORD was hot against Israel; and he said, Because that this people hath transgressed my covenant which I commanded their fathers, and have not hearkened unto my voice;
21 I also will not henceforth drive out any from before them of the nations which Joshua left when he died:
22 That through them I may prove Israel, whether they will keep the way of the LORD to walk therein, as their fathers did keep it, or not.
23 Therefore the LORD left those nations, without driving them out hastily; neither delivered he them into the hand of Joshua.