A chiasm is a literary structure where the words or themes of the first section of a passage are repeated in reverse order in the second. Typically whatever is in the center of the chiasm is what is being emphasized. In the center of Exodus 3:15-16 is Exodus 3:15b-c where God tells Moses that his memorial name to all generations is “The LORD, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob.”