John Calvin on Matthew 13:9

9. He that hath ears to hear, let him hear. These words were intended partly to show that all were not endued with true understanding to comprehend what he said, and partly to arouse his disciples to consider attentively that doctrine which is not readily and easily understood by all. Indeed, he makes a distinction among the hearers, by pronouncing some to have ears, and others to be deaf. If it is next inquired, how it comes to pass that the former have ears, Scripture testifies in other passages, that it is the Lord who pierces the ears, (Psalm 40:7,)and that no man obtains or accomplishes this by his own industry.