5:11 "Him"refers to Melchizedek (v. 10; cf. 6:20-10:18). Evidently the original readers had begun to let their minds wander as they heard the same things repeatedly. Rather than listening carefully, hearing completely, and comprehending clearly, they had become mentally and spiritually dull in their hearing. They were not slow learners but had allowed themselves to grow lazy. A spiritual callus was growing over their ears.
"Deafness or dullness in receptivity is a dangerous condition for those who have been called to radical obedience. The importance of responsible listening has been stressed repeatedly in the sermon (2:1 . . .; cf. 3:7b-8a, 15; 4:1-2, 7b)."162
"One of the first symptoms of spiritual regression, or backsliding, is a dullness toward the Bible. Sunday School class is dull, the preaching is dull, anything spiritual is dull. The problem is usually not with the Sunday School teacher or the pastor, but with the believer himself."163
5:12 Every Christian becomes capable of instructing others when he or she learns the elementary truths of the faith. This is true whether one has the gift of teaching (i.e., the ability to communicate with unusual clarity and effectiveness) or not. However when we fail to pass on what we know we begin to lose what we know. Eventually we may need to relearn the most basic teachings of Scripture. When we stop growing, we start shrinking. We do not just stay the same.
"Christians who have really progressed in the faith ought to be able to instruct others (as 1 Peter 3:15 shows; cf. Rom. 2:21)."164
5:13 Immature babies consume only milk. They cannot chew and assimilate sold food because they are immature. Similarly immature Christians take in only the basics of the gospel because they cannot receive and assimilate the more advanced aspects of the faith. They cannot do this because they have not tried repeatedly (practiced) to understand and apply these more advances truths. This is a pictureof Christians who have been content to know and practice only the most elementary lessons of their faith. They are too lazy to do what is necessary to grow. Of course, even mature adults continue to need milk, which is pre-digested food, but they can also eat solid food.
5:14 The writer's point in these verses is not just that spiritual babies lack information, which they do, but that they lack experience. A person becomes a mature Christian not only by gaining information, though that is foundational, but by using that information to make decisions that are in harmony with God's will. "The word of righteousness"(v. 13) is the solid food that results in righteous behavior. In this context the "solid food"must refer to instruction about the high priestly office of Jesus Christ (cf. 7:1-10:18). Practice is essential for maturity. Consequently a new Christian cannot be mature even though he or she follows the leading of the Spirit (i.e., is "spiritual,"cf. 1 Cor. 2:14-3:3). The readers were in danger of not comprehending what the writer had to tell them because they had not put what they did understand into practice in their lives. Instead, they were thinking of departing from the truth.
"As we grow in the Word, we learn to use it in daily life. As we apply the Word, we exercise our spiritual senses' and develop spiritual discernment. It is a characteristic of little children that they lack discernment. A baby will put anything into its mouth. An immature believe will listen to any preacher on the radio or television and not be able to identify whether or not he is true to the Scriptures."165
This section gives four marks of spiritual immaturity: laziness (dullness) toward the Word (v. 11), inability to teach the Word to others (v. 12), a diet of only elementary truths in the Word (vv. 12-13), and lack of skill in applying the Word (v. 14). As with the muscles in our bodies, if we do not use what we have gained spiritually we will lose it (cf. 2 Pet. 3:18).
