Dan Philips has an excellent article on Matthew 28:19 at Pyromaniacs. Please read it; the details are very important and I would rather you read his article than me having to take the time to repeat what he writes. I have known what Dan says for a long time, but Dan has actually taken the time to write it out and explain it. I could not have written it better.
Dan does an excellent job of rigorous Greek language study, showing that the Aorist participle, “going” has command force, because it is syntactically linked to the main command verb that is in the command/imperative mode – “go and make disciples”. He points us to Dan Wallace’s Greek Grammar Beyond the Basics for confirmation.
The main verb in command/imperative form is “make disciples” or “disciple”.
Dan’s article is much better explaining how the first verbal form “Go” relates to the second verb command, “disciple”. This is much more accurate than the passive sort of way that many have taught this, “as you go”. The first participle, “going” has command force, “go and disciple all nations”. The second two participles (baptizing and teaching) are adverbial participles, seems to be, by context, modifying the main verb, “disciple”, as the methods by which the nations are discipled – “by” – nations are discipled, by baptizing and by teaching. “by baptizing” (which includes preaching and evangelizing; and the nations -ta ethna ( τα εθνη ) where we get the English ideas of ethnicity, ethnic, cultures (ethnities, peoples, people groups, cultures, languages – Revelation 5:9) – also includes culture and language learning as applications.
And the nations cannot be discipled without the going part either, they are also parallel and indicate methods by which we “disciple all nations”:
“Go !” and
Disciple all nations (main verb)
But since the “going” is Aorist, and first, and is linked directly to the command “to make disciples”; then it has that command force and nuance that Dan’s article so excellently explicates.
And part of the “going” includes “sending” by a local, Biblical church –
see Acts 13:1-4 – the church sent them out (verse 3) and the Holy Spirit sent them out.(verse 4)
See also Romans 10:13-15
How shall they hear without a preacher? How shall they preach unless they are sent?