The original reading of the printer’s manuscript reads “save the devil”, an obvious scribal error for “serve the devil”. Oliver Cowdery corrected this error in pencil, which shows that this correction occurred considerably later and probably not when he proofed the printer’s manuscript against the original manuscript. Both save and serve are orthographically similar, which argues that the incorrect save entered the text as Oliver was copying from 𝓞 into 𝓟. We do not have the original manuscript here, but it seems most likely that it read serve. The penciled correction suggests that Oliver made the change while at the 1830 printer’s shop, where pencil rather than ink was normally used to edit the copy-text. Such an emendation at the press would mean that Oliver did not refer to the original manuscript to make this correction—nor did he need to.
Summary: Retain Oliver Cowdery’s emendation of the impossible “save the devil” to “serve the devil”; save is orthographically similar to serve and probably represents a visual error that entered the text (but did not remain long) as Oliver copied from 𝓞 into 𝓟.