Charles Ellicott Commentary Matthew 13:25-26

"but while men slept, his enemy came and sowed tares also among the wheat, and went away. But when the blade sprang up and brought forth fruit, then appeared the tares also." — Matthew 13:25-26 (ASV)

His enemy came and sowed tares—The act described was then, and still is, a common form of Eastern malice or revenge. It easily escaped detection and inflicted both loss and trouble. The “enemy” had the satisfaction of brooding for weeks or months over the prospect of the injury he had inflicted and the vexation it would cause when discovered. The tares, known to botanists as the Lolium temulentum, or darnel, grew up at first with stalk and blade like the wheat; it was not until fructification began that the difference was easily detected. It adds to the point of the parable to remember that the seeds of the tares were not merely useless as food but were positively noxious.