Matthew 13:24
Another parable put He forth unto them, saying, The kingdom of heaven is likened unto a man which sowed good seed in his field:

The subject of this parable is the kingdom of heaven which begins with the sowing of good seed.

[25] But while men slept, his enemy came and sowed tares among the wheat, and went his way.

Notice first that once the enemy sowed "tares" among the wheat... he went his way! The next thing we need to learn is "What are "tares"? For that answer we need to turn to the horticulture of "tares" which we discover is called zizanion (dziz-an'-ee-on) in Greek (#2215) which means "darnel" or false grain :- tares. Here is Dr. Smith's explanation (emphasis ours):

Tares: A noxious plant, of the grass family, supposed to mean the darnel. It grows among the wheat everywhere in Palestine, and bears a great resemblance to it while growing - so closely that, before they head out, the two plants can hardly be distinguished. The grains are found, 2 or 3 together, in 12 small husks, scattered on a rather long head. The Arabs do not separate the darnel from the wheat, unless by means of a fan or sieve, after threshing (Mat. 13:25-30). If left to mingle with the bread, it occasions dizziness, and often acts as an emetic. ("Smith's Bible Dictionary", A. J. Holman Company, pg. 301.)

[26] But when the blade was sprung up, and brought forth fruit, then appeared the tares also.

So we have a field in which both good seed and bad seed were sown and grow together. Do not forget that the Greek word used here for seed is not the same as the one which was used symbolically to represent the Word of God prior to verse 24. This Greek word is "sperma"! Also, it is important to note that only a trained person can distinguish a toxic tare from a true wheat plant while they are growing together in the field, i.e. while the blade is springing up.  However, at harvest time when the fruit appears the two are easily distinguishable one from the other! That makes sense because we know that when we examine fruit we then know what kind of tree or plant produced it.

The bearded darnel (Lolium temulentum) is a poisonous grass, almost indistinguishable from wheat while the two are only in blade, but which can be separated without difficulty when they come into ear (cp. mat. 13:29, 20). ("Davis Bible Dictionary", Baker Book House, pg. 759.)

Now suppose you ARE a trained person and you can tell the difference between the tares and the wheat and you know they have been sown in the field. What should you do about it? Well, even though your first inclination is probably to go root up the tares, as a wise servant of the householder you would surely not take it upon yourself to go meddling in the field with your own solution to the problem without first going to the householder to see how he wants to handle it, would you? Hopefully not for in this case if you rooted them up you would be working against the will of the householder. Wisdom would dictate that you go to him first and ask him what you should do about them?

[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?

We see that the "servants" of the householder knew there were tares, toxic look-alike false wheat plants, in the field!

[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?

Hmmm, it seems the sowing of the tares was the deliberate covert activity of the enemy. Again, one's first thought might be to rush out and pluck up those suckers. However, when the servants went and ask the householder if they should go and gather them up (which was what they were inclined to do), here is His direct answer... "NO"! So take an object lesson from this and remember to first learn the plan of God, His will, and then do things His way or He might just have to find another servant who is willing to do so!

[29] But he said, Nay; lest while ye gather up the tares, ye root up also the wheat with them.

Let the tares alone! Remember this well, for when we learn who the tares represent, then the literal application of this instruction will be evident. Now here is the householder's further instruction concerning the tares.

[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.

Let them alone "until the harvest" ( the end of this earth age when Christ returns) lets us know that this instruction is given even to this final generation and applies right now as well as in the future. So make no mistake about it! The will of the householder is that we "Leave the tares alone!"  All we still need to learn yet is what or who the tares represent. So hang in there because we are about to learn the mystery, which is actually the simple meaning, of the parable of the tares as it relates to God's Plan in the kingdom of heaven. Again, it cannot be emphasized enough that what we have just read so far from Mat. 13:24-30 is only a parable, which if you recall is "a truth expressed in similitude using symbols with characteristics analogous to something else". And most Christians, who comprise the multitudes today, do not understand this parable for as we shall see when we get to verse 34, its "secret" has been kept just that, secret (hidden) from the "foundation of the world"! And so it is to this day that because the multitudes are Biblically illiterate and are therefore not "trained" in the Word of God as disciples (students) of Christ, they cannot tell the difference between a tare and a wheat plant.In fact, they do not even know of the sowing of the "sperma" that has taken place in the field!