Mark 4:13-15 - Don't you understand this parable?

4:13

Now Jesus turns to His disciples, “Don’t you understand?”, adding “How then will you understand any parable?”. This could be taken as saying understanding this parable is a key to understanding all the parables, or it could be a general commentary on the state of the disciples.  Jesus then goes on to explain the parable.

4:14,15

First we learn that the seed is the word of God. The word of God has the potential to produce much fruit, but its effectiveness is dependent upon the state of the soil. The seed that was sown on the path was like the case where people hear the word, but immediately Satan comes in and takes away the word. He can do this by immediately countering what was said, or by distracting them into paying attention to something else. Note that Jesus says “Satan comes ...” Sometimes people try to be clever by saying that Satan is not omnipresent (which is true), so he cannot be everywhere and putting things down to Satan is wrong. It is indeed true that Satan is not omnipresent, but his work is all over the world, so this argument is just trying to be too clever.