In the text, three things are hinted at by Christ with respect to the presence of evil among the good.
I. Here, first, is the secrecy, the undiscernibleness of its beginnings "while men slept;" words which could hardly have been meant to indicate negligence or inattention on the part of those who should have been alert and watchful, and whose vigilance might have prevented the hostile sowing, since the servants, who later on ejaculate their astonishment and disappointment at what is found among the corn, are in nowise charged with having contributed to it by omission of duty. The words were intended, doubtless, as an equivalent for during the night, during the interval when men are naturally wrapt in slumber and cannot perceive what is done. The Speaker would be suggesting thus, with a passing touch, how hidden and unobserved are the beginnings of evil; how, in regard to its first startings and earlier motions, we are like them that sleep.
II. But here, again, is the facility with which it grows, its independence of fostering care or aid. "He went his way." Was not that a stroke of the artist, with which He meant to intimate the little that is needed to insure the progress and spread of evil? The enemy just sowed and went his way. What he had sown was safe to grow. Noxious weeds want no watering. Good habits have to be formed with stern endeavour and in the sweat of your brow; bad habits form themselves as we stand idly by.
III. Here is the inevitable following of evil in the wake of good; the inevitableness of its accompaniment and concurrence for a season wherever good is sown. This is what Christ prognosticated would happen that His sowing of wheat would involve a sowing of tares. And has it not been so? With all the devotion and consecration, with the splendid courages, zeals, and self-sacrifices, which He has inspired, what bitterness and uncharitableness, what dissensions and animosities, what sourness and meanness have mingled! What Christ forebodes here are the evils incident to the very spirit of Christianity.
S. A. Tipple, Sunday Mornings at Norwood,p. 339.