He said unto him, What is written in the Law? The Lord replied, perhaps pointing to one of the phylacteries which the lawyer wore on his forehead and wrist. These phylacteries were little leather boxes (the dimensions of these varied from the size of an ordinary hazelnut, to that of a large walnut, and even in some cases much larger).
In these leather boxes were little parchment rolls containing certain texts from the Pentateuch. Certainly the first of the two great rules, that concerning God, was one of these texts (Deuteronomy 6:5); possibly, but not certainly, the second concerning the neighbour formed another text.