¹³ For everyone who partakes only of milk is not accustomed to the word of righteousness, for he is an infant.

Basic principles of Christian growth depicted by analogy of human growth from infancy to maturity—this captures succinctly the truth that readers of this letter needed to hear, including us today. A number of observations will lead us to the dynamic relevancy of this passage.

First, spiritual growth is centered on “the Word” (although our translation – the NASB – does not capitalize this word, we follow the often used convention of doing so for distinguishing clearly the reference to Scripture). There can be no spiritual growth without knowledge of the Word of God. Remember, in Hebrews 1:1-2 the foundation of the truth in this letter is found in the fact that “God spoke.” We know generally about God in nature, but only through His revealed and written communication do we have the substance, instructions, guidance and tools for building our spiritual lives. The Holy Spirit, to be sure, enables us and empowers us, but it is through the Word of God that He enlightens, and provides the knowledge of Him.

Without the written Word, we are left to the changing emotions and cogitations of the human mind, which experience shows is quite fickle. Such produces infants—there is no growth. People like that are immature, and likened to a full grown adult (physically) who still nurses at his mother’s breast. There is certainly a shock value in that imagery. It’s absurd, obscene. So too, is a Christian who continues in a state of spiritual infancy.

Second, the Word is described as “the word of righteousness.” We are not talking here about intellectual understanding that produces knowledge only. The issue is not how much a person knows, but how much they live out what they know. The most obvious form of spiritual immaturity is the person who simply does not spend much time reading the Word. He never pushes to go beyond the basics. He is not like the seed that falls on good soil, whose roots go deep (Luke 8:5-8). He is not like the tree that is planted by the waterside: “… which yields its fruit in its season and its leaf does not wither; and in whatever he does, he prospers” (Ps 1:3). This person might be able to find John 3:16 in the Bible, but that is about it! Almost all of what they know is what the preacher says on Sunday. They enjoy being bottle-fed.

Another kind of spiritual immaturity is when a person knows a considerable amount of Bible truth, but does not customarily live according to that truth.