Vincent's NT Word Studies
38. Refrain (aposthte). Lit., stand off.Of men (ex anqrwpwn). Out of men, proceeding out of their devices. It will come to naught (kataluqhsetai). Lit., be loosened down. Used of the dilapidation of the temple (Luke xxi. 6), and of the dissolution of the body under the figure of striking a tent (2 Cor. v. 1). See on Mark xiii. 2.
Robertson's NT Word Studies
5:38 {Refrain from} (apostete apo). Second aorist (ingressive) active imperative of afistemi of verse #37. Do ye stand off from these men. "Hands off" was the policy of Gamaliel. {For if--be} (hoti ean--ei). 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 i, undetermined with prospect of determination. Assuming that it is from men, "it will be overthrown" (kataluqesetai, first future passive of kataluw, to loosen down like a falling house) as was true of the following of Theudas and Judas the Galilean.