There's nothing new under the sun. I think Ecclesiastes says that a time or two. As I was pinch hitting for a friend last night at the jail I found myself speaking to a crowd of about a dozen or so of the guys I've previously spoken to during the addictions class.
Not having any say in who my audience would be I knew not who I was going to be speaking to. I had not a tremendous amount of time to prepare and eventually I found myself in front of this group, most of whom I've already spoken to multiple times. My material was a conglomeration of notes from the previous jail addictions class and scriptures used therein as well.
I had a few minutes to consider flinging together an alternate message. It finally seemed unnecessary. In spite of the fact that the majority of the group had heard this material covered (although there were a couple new faces) the Gospel seemed to me entirely sufficient. Again I was conscious of the Scriptural truth that God's Word never goes forth void.
It was humbling to admit before that group that I had not known I would be speaking to them and I had not much time to prepare. Again I was made aware that God alone is the one Who changes people and His Word is incredibly powerful.
So I found myself without original material. I was reminded of somebody (I think it was Tozer, but I could be wrong) who said, "If anything in Christianity is new, it is by the same token false." It is not necessary for something to be new in order for it to be effective.
Thousands of years old. Hundreds of books have been written about it. Unknown multitudes have spent their entire lives learning about it and teaching it. Completely unoriginal but always radically powerful... That's precisely what the Gospel is.