Unless you are Jesus Christ all sermons should be Scripture reading and no human commentary at all, no? I mean once you leave Scripture you have entered interpretation, and that is either error or not.
If one is concerned about error, stop preaching once interpretation starts. If one is not concerned about error and has faith, that God will lead one in the truth necessary, it does not matter if humans condemn you for heresy. It is God you answer to, not man.
There is nothing wrong with attempting to explain in more detail Scripture. That is not adding to God's Word. The problem comes when a person claims Scripture is wrong, and attempts to give a more human understanding than what God has given. If one is going to constantly correct God's Word, may as well use any book to preach from.