{Do thyself no harm} (m(8864)en prax(8869)s seaut(9369) kakon). The
usual construction (m(885c) and the aorist subjunctive) for a
prohibition not to {begin} to do a thing. The older Greek would
probably have used poi(8873)(8869)s here. The later Greek does not
always preserve the old distinction between poie(935c), to do a
thing, and prass(935c), to practice, though prassete keeps it in
 Php 4:9  and poie(935c) is rightly used in  Lu 3:10-14 . As a
matter of fact prass(935c) does not occur in Matthew or in Mark,
only twice in John, six times in Luke's Gospel, thirteen in Acts,
and elsewhere by Paul. {Sprang in} (eisep(8864)(8873)en). First aorist
active of eisp(8864)a(935c), old verb, but here only in the N.T. Cf.
ekp(8864)a(935c) in  14:14 . The jailor was at the outer door and he
wanted lights to see what was inside in the inner prison.