Jamieson, Fausset & Brown

if ye believe not that I am he, ye shall die in your sins--They knew well enough what He meant (Mar 13:6, Greek; compare Mat 24:5). But He would not, by speaking it out, give them the materials for a charge for which they were watching. At the same time, one is irresistibly reminded by such language, so far transcending what is becoming in men, of those ancient declarations of the God of Israel, "I AM HE" (Deu 32:39; Isa 43:10, Isa 43:13; Isa 46:4; Isa 48:12). See on Joh 6:20.