What does Jesus mean when he says,

Take care then how you hear, for to the one who has, more will be given, and from the one who has not, even what he thinks that he has will be taken away (Luke 8:18)?

He is applying the parable of the four soils (Luke 8:12-15). Notice the connection between “take care how you hear,” and the focus in hearing in the parable.

1. “The ones along the path are those who have heard; then the devil comes and takes away the word.”
2. “And the ones on the rock are those who, when they hear the word, receive it  with joy. But these have no root; they believe for a while, and in time of testing  fall away.”
3. “And as for what fell among the thorns, they are those who hear, but  as they go on their way they are choked by the  cares and riches and pleasures of life.”
4. “As for that in the good soil, they are those who, hearing the word, hold it fast in an honest and good heart, and bear fruit  with patience.”

The point of that parable is that three out of four ways to “hear” result in the word being “taken away.” So Jesus says, “Take care how you hear.” It is infinitely important whether we hear like the three soils and lose what we heard, or hear like the fourth soil and bear fruit with what we heard.

Jesus motivates us to “take care how you hear” by saying two things, the first relating to the fourth soil, the second relating to the first three soils.

1. “. . . for to the one who has, more will be given. . .”
   
   When we hear and “hold it fast in a honest and good heart,” we bear fruit. That is, more [fruit] is given to those already have [the word held fast by an honest and good heart].

2. “. . . and from the one who has not, even what he thinks that he has will be taken away.”
   
   The first three ways of hearing are deceived. They “think” they have the word, but they don’t. And even this illusion will be destroyed some day: “What he thinks that he has will be taken away.”

When you hear preaching or read your Bible take hold of it like a miser taking hold of gold and silver. Take hold of it like a pearl of great price and a treasure in a field. Take hold of it like a drowning man seizes a float. Fight off every word-destroying demonic bird and burning affliction and deceitful desire. Then you will “have” and “more will be given.” You will bear fruit with patience.