1 Samuel 16:10

Again (or rather, Thus) Jesse made seven of his sons to pass before Samuel Not all at once, but seven in all, one after another, in order, David being the eighth. See 1 Samuel 17:12. Probably, however, one of these was either only an adopted son, or was born of a concubine, and therefore is not noticed 1 Chronicles 2:13; 1 Chronicles 2:15, where only seven of Jesse's sons are named, and David is said to have been the seventh. Samuel said unto Jesse, The Lord hath not chosen these These words show that Samuel had acquainted Jesse with his business.