Great question and responses.
Here are a few of candidates for what "sound doctrine" can mean.
Hebrews 5:12-14 (KJV)
12 For when for the time ye ought to be teachers, ye have need that one teach you again which
be the
first principles of the oracles of God; and are become such as have need of milk, and not of strong meat.
13 For every one that useth milk
is unskilful in the
word of righteousness: for he is a babe.
14 But
strong meat belongeth to them that are of full age,
even those who by reason of use have their senses exercised to discern both good and evil.
Though not exactly sound doctrine itself, this scripture struck me as how there are different versions, and different deliveries from men teaching or preaching the word.
Mark 1:22 (KJV)
22 And they were astonished at his
doctrine: for he taught them as one that had authority, and not as the scribes.
Here is Strong's definition of authority.
exousia
from
<G1832> (exesti) (in the sense of
ability);
privilege, i.e. (subject)
force, capacity, competency, freedom, or (object)
mastery (concrete
magistrate, superhuman, potentate, token of control), delegated
influence :- authority, jurisdiction, liberty, power, right, strength.
Too often people teach and preach the word and it is not mixed with the heart and mind of God, but rather the dryness of theology or man's own meaning. Such doctrine can still be right but in addition to merely saying something, God (at least to many) still demonstrates the power of his Spirit. Good doctrine can be conveyed in a manner that is dynamic, influential, and demonstrates the power of God. Though this does not define sound doctrine it does help us to recognize when it is given. Of course, it has to align with the word and bear witness too.
1 Corinthians 2:3-5 (KJV)
3 And I was with you in weakness, and in fear, and in much trembling.
4 And my speech and my preaching
was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power:
5 That your faith should not stand in the wisdom of men, but in the power of God.
Zodhiates word study shows that doctrine is associated with how something is taught as well as the content. Note too there are two different but similar words for doctrine in the bible.
"Essentially
didaché is the same as
didaskalía <G1319>, sometimes meaning the manner of teaching and sometimes the content of teaching. Both are used in the act. and pass. senses, i.e., the act of teaching and the content of what is taught. However, it is to be noted that the pass. sense is predominant in didaché and the act. sense in didaskalía. In didaché, we have incorporated the authority of that which is taught, and didaskalía predominates in the act or art of teaching. Didaché is used only twice in the Pastoral Epistles (
2 Tim. 4:2;
Titus 1:9) while didaskalía, with a stress on the art of teaching, occurs fifteen times."
Complete Word Study Dictionary,