Expositor's Bible Commentary Commentary Mark 4:27

"and should sleep and rise night and day, and the seed should spring up and grow, he knoweth not how." — Mark 4:27 (ASV)

This parable emphasizes the mysterious power of the seed to produce a crop. All the farmer can do is plant the seed on suitable ground; he cannot make the seed grow, nor does he understand how it grows. But it does grow and produces grain. In the same way, the hidden and somewhat ambiguous kingdom of God will some day burst out in its full glory. The harvest spoken of is the eschatological judgment (cf. Joel 3:13).