Hebrews 5:13

‘For every one who partakes of milk is without experience of the word of righteousness, for he is a babe.’

Being those who are partaking of milk and not meat demonstrates that they are without experience of the ‘word of righteousness’. ‘The word of righteousness’ is probably intended to cover all aspects of righteousness as it pertains to God and His people. For God’s purpose is that His people be both accounted righteous and made righteous. Both are in the end part of one process, part of the righteousness of God. Those who but drink milk have no experience of the teachings concerning the righteousness of Christ as it applies to His people, both as imputed and imparted. They know nothing of justification, sanctification and growth in righteousness, of the deeper significance of the cross as a provider of righteousness and crucifier of the flesh, and thus no knowledge of the High Priesthood of Christ. They only know about the very basics of such things as sin and repentance, and general faith towards God, and outward ceremonies, and general resurrection and judgment (Hebrews 6:1-2). And this demonstrates that they are still totally dependent babes at the breast. Compare Ephesians 4:13-16; 1 Corinthians 3:1-3.