For every one that partaketh of milk is unskillful in the word of righteousness: for he is a babe. Reason for saying that they are such as have need of milk; for milk is the nourishment of infants, and he that is an infant in respect of spiritual growth is ἄπειρος λόγου δικαιοσύνης: not of necessity unacquainted with it altogether, but still not versed in it; he is but a tyro.
"Word of righteousness" may be taken as a general term to denote what we might call religious lore; referring here especially to the gospel, which is eminently the revelation of the "righteousness of God" (Romans 1:17; cf.
2 Corinthians 3:9, ἡ διακονία τῆς δικαιοσύνης: and 2 Corinthians 11:15, διάκονοι δικαιοσύνης); but not excluding a more general conception. There is no need to suppose an exclusive reference to the more perfect doctrine in opposition to the elements, since, of the whole subject of religious knowledge, the νήπιος may be said to be ἄπειρος in the sense of being without the matured skill that experience gives.
Hence, too, we are certainly not justified in finding in the phrase a specific allusion to the Pauline doctrine of justification by faith only, which is not suggested by the context or by what follows.
Still less may we (with Delitzsch) so ignore the notable significance of δικαιοσύνη as to reduce the expression to a synonym for "rightly framed, that is sound and orthodox discourse."