The good seed is sown: that is God's blessed indestructible work. The enemy sows tares: that is Satan's work. Note that the enemy's work was done “while men slept.” Thus it has ever been that man fails when responsible in God's things.
Note, too, that the wheat and the tares are individuals. This brings out the outward aspect of the Kingdom in that Satan has succeeded in introducing mere professors into the Kingdom.
Many Christians think this Scripture warrants them in sitting down with the unconverted at the Lord's supper, seeing that the exhortation is to let both wheat and tares grow up till the time of harvest, and not to pull up the tares at once. But the field is the world, and not the assembly. This contention thus falls to the ground.
Doubtless the true children of the Kingdom today are also true members of the Church of God. But the Church of God is the place of holy discipline, where no unconverted person should have the privilege of the Lord's supper. The exhortation to let both wheat and tares grow together to the end does not refer at all to the discipline of the Church, but to the deferring of judgment until the time of the end. The time of harvest refers to the moment when Christ shall set up His Kingdom in display.