Do not therefore yield unto them (Su oun mē peisthēis autois). First aorist passive subjunctive of peithō, common verb, here to be persuaded by, to listen to, to obey, to yield to. With negative and rightly. Do not yield to them (dative) at all. On the aorist subjunctive with mē in prohibitions against committing an act see Robertson, Grammar, pp. 851-4.
For there lie in wait (enedreuousin gar). Present active indicative of enedreuō, old verb from enedra (Act 23:16), in the N.T. only here and Luk 11:54 which see.
Till they have slain him (heōs hou anelōsin auton). Same idiom as in Act 23:12save that here we have anelōsin (second aorist active subjunctive) instead of apokteinōsin (another word for kill), “till they slay him.”
Looking for the promise from thee (prosdechomenoi tēn apo sou epaggelian). This item is all that is needed to put the scheme through, the young man shrewdly adds.