While men slept, his enemy came - That is, "in the night," when it could be done without being seen, an enemy came and scattered bad seed on the new-plowed field, perhaps before the good seed had been harrowed in.
Satan thus sows false doctrine in darkness. In the very place where the truth is preached, and while the hearts of people are open to receive it, by false but plausible teachers he takes care to inculcate false sentiments. Often it is one of his arts, in a revival of religion, to spread secretly dangerous notions of piety. Multitudes are persuaded that they are Christians who are deceived. They are awakened, convicted, and alarmed. They take this for conversion. Or they find their burden gone; they fancy that they hear a voice; or a text of Scripture is "brought" to them, saying that their sins are forgiven; or they see Christ hanging on the cross in a vision; or they dream that their sins are pardoned, and they suppose they are Christians. But they are deceived. None of these things are any conclusive evidence of piety. All these may exist, and still there be no true love to God or Christ, and no real hatred of sin and change of heart. An enemy may do it to deceive them, and to bring dishonor on religion.
Sowed tares - By "tares" is probably meant a degenerate kind of wheat, or the darnel-grass growing in Palestine. In its growth and form it has a strong resemblance to genuine wheat; but it either produces no grain, or that of a very inferior and hurtful kind. Probably it comes near to what we mean by "chess." It was extremely difficult to separate it from the genuine wheat, on account of its similarity while growing.
"The tare abounds all over the East, and is a great nuisance to the farmer. It resembles the American "cheat (chess)," but the "head" does not droop like cheat, nor does it branch out like oats. The grain, also, is smaller, and is arranged along the upper part of the stalk, which stands perfectly erect. The "taste" is bitter, and when eaten separately, or even when diffused in ordinary bread, it causes dizziness, and often acts as a violent emetic. Barn-door fowls also become dizzy from eating it. In short, it is a strong soporific poison, and must be carefully winnowed, and picked out of the wheat grain by grain, before grinding, or the flour is not healthy. Even the farmers, who in this country generally "weed" their fields, do not attempt to separate the one from the other. They would not only mistake good grain for them, but very commonly the roots of the two are so intertwined that it is impossible to separate them without plucking up both. Both, therefore, must be left to "grow together" until the time of harvest." - (Thomson) "The Land and the Book," vol. ii. pp. 111, 112. Thus, "tares" aptly represented hypocrites in the church. Strongly resembling Christians in their experience, and, in some respects, their lives it is impossible to distinguish them from genuine Christians, nor can they be separated until it is done by the Great Searcher of hearts at the day of judgment. An enemy the devil hath done it. And nowhere has he shown profounder cunning, or done more to adulterate the purity of the gospel.
And went his way - There is something very expressive in this. He knew the soil; he knew how the seed would take root and grow. He had only to sow the seed and let it alone. So Satan knows the soil in which he sows his doctrine. He knows that in the human heart it will take deep and rapid root. It needs but little culture. Grace needs constant attendance and care. Error, and sin, and hypocrisy are the native products of the human heart, and, when left alone, start up with deadly luxuriancy.

But while men slept - When the professors were lukewarm, and the pastors indolent, his enemy came and sowed tares, ζιζανια degenerate, or bastard wheat. The righteous and the wicked are often mingled in the visible Church. Every Christian society, how pure soever its principles may be, has its bastard wheat - those who bear a resemblance to the good, but whose hearts are not right with God. He who sows this bastard wheat among God's people is here styled God's enemy; and he may be considered also as a sower of them who permits them to be sown and to spring up through his negligence. Wo to the indolent pastors, who permit the souls under their care to be corrupted by error and sin! This word does not, I believe, occur in any of the Greek classics, nor in Dioscorides; but it may be seen in the Geoponica, or Greek writers De Re Rustica: see the edition by Niclas, vol. i. lib. ii. c. 43, where το ζιζανιον is said to be the same which the Greeks call αιρα; and Florentinus, the author, says, Το ζιζανιον, το λεγομενον Αιρα, φθειρει νον σιτον, αρτοις δε μιγνυμενη, σκοτοι τους εσθιοντας. "Zizanion, which is called αιρα, darnel, injures the wheat; and, mixed in the bread, causes dimness of the eyes to those who eat of it." And the author might have added vertigo also. But this does not seem to be the grain to which our Lord alludes.
The word ζιζανια, zizania, which is here translated tares, and which should rather be translated bastard or degenerate wheat, is a Chaldee word; and its meaning must be sought in the rabbinical writers. In a treatise in the Mishna called Kelayim, which treats expressly on different kinds of seeds, the word זונים zunim, or זונין zunin, is used for bastard or degenerated wheat; that which was wholly a right seed in the beginning, but afterwards became degenerate - the ear not being so large, nor the grains in such quantity, as formerly, nor the corn so good in quality. In Psalm 144:13, the words מזן אל זן mizzan al zen, are translated all manner of store; but they properly signify, from species to species: might not the Chaldee word זונין zunin, and the Greek word ζιζανια, zizania, come from the psalmist's זנזן zanzan, which might have signified a mixture of grain of any kind, and be here used to point out the mixing bastard or degenerate wheat among good seed wheat? The Persic translator renders it telkh daneh, bitter grain; but it seems to signify merely degenerate wheat. This interpretation throws much light on the scope and design of the whole passage. Christ seems to refer, first, to the origin of evil. God sowed good seed in his field; made man in his own image and likeness: but the enemy, the devil, (Matthew 13:39), corrupted this good seed, and caused it to degenerate. Secondly, he seems to refer to the state of the Jewish people: God had sowed them, at first, wholly a right seed, but now they were become utterly degenerate, and about to be plucked up and destroyed by the Roman armies, which were the angels or messengers of God's justice, whom he had commissioned to sweep these rebellious people from the face of the land. Thirdly, he seems to refer also to the state in which the world shall be found, when he comes to judge it. The righteous and the wicked shall be permitted to grow together, till God comes to make a full and final separation.

But while men slept,.... Good men, ministers, and churches; whose case this sometimes is to be asleep in a spiritual sense: and which sleepiness lies in a non-exercise of grace; in a sluggishness to and in duty; in a contentment in external exercises of religion; in lukewarmness about the cause of Christ; in an unconcernedness about sins of omission and commission; and in a willingness to continue in such a state; and which arises from a body of sin and death; from worldly cares; weariness in spiritual duties; a cessation from spiritual exercises; an absenting from spiritual company; oftentimes from outward ease, peace, and plenty, sometimes from a long expectation of the bridegroom's coming, and the delay of it; and from its being a night season, a time of darkness and security: such a case with the church, and good men, is very dangerous, as it exposes to every sin and snare; renders them liable to lose the presence of Christ, their liveliness and comfort; and tends to poverty and leanness of soul: such are in danger of being surprised with the midnight cry; and the churches are likely to be filled with hypocrites and heretics:
his enemy came; by whom is meant the devil, Matthew 13:39 who is an enemy to Christ personally, and showed himself to be so in his infancy, by stirring up Herod to seek his life: and, when grown up, by instigating the Jews to contrive his death; which they attempted by various methods, and which, at last, he compassed by Judas, and the Scribes and Pharisees; and also to Christ mystical, to the church, and all true believers; whose adversary he is, going about, like a roaring lion, seeking whom he may devour: the same came into the field, the world, and church in it;
and sowed tares among the wheat; by "the wheat", is meant the same with the "good seed", the children of God, true believers in Christ; who are comparable to wheat, for the choiceness of it, that being the choicest grain, so they are the chosen of God, and precious, and the excellent in the earth: and because it dies before it rises and springs up; so the saints do, and will do, both in a spiritual and corporal sense; and because of the purity and whiteness of it, so they are pure and white, being sanctioned by the Spirit, washed in the blood of Christ, and justified by his righteousness; and because of its substance, fulness, weight, and permanence, so they are filled from Christ's fulness, and with the fulness of God, and fruits of righteousness, and remain, and cannot be driven as the chaff is, but continue to live, because Christ their head lives; and because of its gradual increase, so they increase in spiritual light, grace, and experience; and because of the chaff that adheres to it, so sin and corruption cleave to the saints in this life; and lastly, because it needs both the flail and the fan, so believers need chastisements, afflictions, and corrections: by "the tares" sown among them, are meant "the children of the wicked one"; Satan, the enemy and adversary, as in Matthew 13:38 who are to be understood, not of profane sinners; though these are the children of the devil; but of professors of religion, men either of bad principles, or of bad lives and conversations; whom Satan, by some means or another, gets into churches, and they become members thereof: at first they look like wheat, like true believers, have a show of religion, a form of godliness, an appearance of grace, but are destitute of it; and prove tares, unfruitful, unprofitable, and of no account, yea hurtful, and whose end is to be burned.
And went his way; somewhere else, to do more mischief; and having done all he could at present here, undiscovered, not taken notice of by ministers and churches; they being all asleep, and having lost, in a great measure, the spirit of discerning. The word we render "tares", and the Ethiopic version "thistles", probably means the same the Jewish doctors call Zunin (s); and which, they say, is a sort of wheat, and not of a different kind from it; that when it is sown it looks like wheat, and is sown for it, but is changed in the earth, both as to its nature and form, and brings forth this kind. In the generation in which the flood was, they say (t), they sowed wheat, and the earth brought forth what we render "tares", and bids fair to be what is here meant; and fitly expresses false professors, nominal Christians, men of degenerate principles and practices: for not what we call tares, or vetches, can be meant, which may be removed from the wheat without danger, but rather this degenerate wheat; or that wheat which is blasted, and which may be observed sometimes to grow upon the same root, and therefore cannot be taken away, without rooting up the wheat also.
(s) Misn. Kilaim, c. 1. sect. 1. & Trumot, c. 2. sect, 6. & Maimon. in ib. T. Hieros. Kilaim, fol. 26. 4. Maimon. Hilch. Kilaim, c. 3. sect. 3. (t) Bereshit Rabba, sect. 28. fol. 23. 4.

But while men slept, his enemy came and sowed tares among the wheat, and went his way--(See on Matthew 13:38-39).

But while men slept. During sleep is the time of the tare-sowing.
His enemy came and sowed. It is by no means uncommon for the malice in the East to show itself in this way. A wicked person may do great injury with little chance of detection.
Tares. The tare or darnel is, like our chess or cheat, a kind of bastard wheat, looking like wheat.

But while men slept - They ought to have watched: the Lord of the field sleepeth not. His enemy came and sowed darnel - This is very like wheat, and commonly grows among wheat rather than among other grain: but tares or vetches are of the pulse kind, and bear no resemblance to wheat.