An excerpt from the Work of St. John Chyrsostom

What is the difference between this and the preceding parable? In the first He speaks of those who hearkened not to Him, turning away, and rejecting the good seed.  Here He speaks of heretics. He foretold this also lest later HIs Disciples might be troubled regarding this very matter.  The parable that precedes this refers to those who did not receive His Word.  This speaks of those who receive the corruptors of His Word. For it is the guile of the spirt of evil to commingle his own errors with the sowing of the truth, so that they have the shape and color of truth, and so deceive the trusting.  He then here speaks not of any seed, but only of tares, which resemble wheat.

Then He speaks of the manner of this guile, while men are asleep. Here lies no small danger of headlong disaster for the rulers of the Church, to whom has been confided the care of the field; and not only to the rulers, but to the subjects as well. He shows here very clearly that wherever the seed of truth has been sown, error follows after, as events have truly confirmed.  For after the Prophets have come the pseudo-prophets; after the apostles the pseudo-apostles; after Christ anti-Christ.