I beseech you, therefore, do nothing in a spirit of division, but according to Christian teaching. Indeed, I heard some men saying: "If I do not find it in the official records in the gospel I do not believe." And when I made an answer to them, "It is written!" they replied, "That is the point at issue."
But to me, the official records are Jesus Christ; the inviolable record is His cross, His death, and His resurrection, and the faith which He brings about: in these I desire to be justified by your prayers.
This passage underscores that even in 110 AD, there were people who mistakenly followed the doctrine of sola scriptura. So it wasn't Luther's invention after all. Jurgens (the editor) explains that the question may actually be related to whether something appears in the Old Testament as well as the New. However, even the history of Judaism, you have the Pharisees (those who believed in an oral tradition or Oral Law, the Talmud) and the Saduccees (those who did not accept anything other than the written word).