{Refrain from} (apost(8874)e apo). Second aorist (ingressive)
active imperative of aphist(886d)i of verse  37 . Do ye stand off
from these men. "Hands off" was the policy of Gamaliel. {For
if--be} (hoti ean--(8869)). Hoti gives the reason for the advice.
Gamaliel presents two alternatives in terms of two conditional
clauses. The first one is stated as a condition of the third
class, ean with the present subjunctive (8869), undetermined with
prospect of determination. Assuming that it is from men, "it will
be overthrown" (kataluth(8873)etai, first future passive of
katalu(935c), to loosen down like a falling house) as was true of
the following of Theudas and Judas the Galilean.