Ezra listened, and thought he vaguely remembered scenes in old westerns or whatever, of people sharpening or caring for a straight razor. But he didn't know what he would need, or anything else. He considered everything, pausing to test the blade against the backside of his wrist, which caught, and he barely managed not to actually cut himself.
Looking back to Mort, his expression wary, he asked the relevant question. "...why would you do that?" he asked. It wasn't pointed - he wasn't meaning to be a jerk about it or anything, it was something he honestly wanted to know. "...what do you want from me in return?"