Learning Greek and Hebrew is fun. Well, perhaps hammering paradigms and vocab into your brain isn't the most glamourous of study but the results are invaluable. One of the many ways having a working knowledge of Greek and Hebrew can impact you is in the sermon preparation. You're able to see the subtle nuances of meaning that don't come across as plainly in the English text (or whatever language you are reading). That's an exciting thing. So exciting, in fact, that it wells up in not only sermon preparation but sermon delivery.
This is for a good reason as there is much that a congregation can gain from a pastor explaining various Greek and Hebrew terms in a given text. However, this can go really wrong really fast. If we aren't aware of how to properly communicate Greek and Hebrew in preaching, we may be doing more harm than good. Allow me to offer three pieces of humble advice in this.
Don't Show All Your Homework
I want to restate my point that congregations can gain a lot from their pastor explaining the Greek and Hebrew. However, just because it is interesting to you (and was edifying to you) doesn't mean it needs to be in the sermon. That is to say, that shouldn't be the only qualifier for its entry into your sermon. Certainly it can be a qualifier but if the point you would make in talking about the futuristic use of the aorist tense doesn't stand to establish your greater homiletical point, perhaps it is best to leave that comment out.
Don't Overestimate or Underestimate the Congregation
When it comes to interacting with the original languages in preaching, a lot of it depends on one's audience. There is the risk of overestimating the congregation in which the vocabulary you use in describing concepts that arise in the original languages is overly academic (in truth, this issue can exist no matter the congregation). There is also the perhaps greater risk of underestimating the congregation. I recall a time where I was practicing an upcoming sermon on Col 1:15-20 in front of a friend and I had begun to describe Jesus as the necessary being and us his creation as contingent beings. My entry into that comment was something along the lines of, "Now this is going to seem pretty weighty and confusing but I promise you'll be able to see the significance of this".
I thought I was doing the congregation a favor by assuring them that it was okay if they hadn't heard of these concepts before when in actuality, as my friend advised I consider, an introductory statement like that would likely be received as, "this is too complicated for you but I'll dumb it down". I took that advice and altered my statement. We do a service to a congregation to be considerate that they may not have the vocabulary to interact with original language matters but also not insult their intelligence.
Don't Say "What It Really Means Is..."
Before you crucify me, let me explain. Those who have background in Greek and Hebrew know that the practice of Bible translation is both a science and an art. There come times when a translator is forced to make a decision as the meaning of a phrase could go one or two different ways. And so, as we read the Greek and Hebrew we will come across texts where we think, "I'm not sure I would have translated it that way". That's a fine instinct to have and requires considerable discernment. However, it is a risky thing to communicate in a sermon.
Now, the objective here is not to cover something up about the original text so that the congregation doesn't know about it. Rather, we want to instill a justified confidence in their English Bibles. And so, when a pastor says "What this really means..." they are letting off a grenade that they may not be prepared to diffuse. Certainly those who are acquainted with the original languages know how to unpack a statement like that. The average congregant... not so much. And so what can oftentimes take place is a pastor says a statement like that forcing the congregant to rightly ask "If it really means that, why isn't it in my Bible." Thus, the pastor has sparked a greater problem than he intended to solve.
This is not to say that the pastor should never explain the nuances of meaning that occur in the original languages. However, the pastor does right by the congregation in considering how his explanation may instill more doubt than confidence.