1 Chronicles 29:29

They are written in the book of Samuel the seer In the two books of Samuel, as they are now called, which were written in part by Samuel while he lived, and continued after his death by Nathan and Gad. And in the book of Nathan, and the book of Gad In the public registers, or chronicles of the kingdom, which were written by Nathan and Gad, who were not only prophets, but historiographers, out of which, either they or some other prophets took, by the direction of God's Spirit, such passages as were most important and useful for the churches in succeeding ages.