Mark 4:23

If any man have ears to hear, let him hear.

The call is to give real heed to Jesus' instruction and to seek to understand it. The measure of sincere attention given determines the measure of knowledge received. Those who sincerely receive his truth and desire it gain greater knowledge and light and benefit from their God-given privileges. Those who reject the truth lose even the little understanding and knowledge they have. What is heard is to be shared with others, and whether the teaching has taken root in the heart is eventually shown by a person's actions and fruit.