They went out from us, but they didn't belong to us; for if they had belonged to us, they would have continued with us. But they left, that they might be revealed that none of them belong to us.

 But that is neither the commonest nor the most literal sense of parakalein ( G3870) ; its commonest sense is to call someone to one's side in order to use him in some way as a helper and a counsellor. In ordinary Greek that is a very common usage. Xenophon (Anabasis 1.6.5) tells how Cyrus summoned (parakalein, G3870) Clearchos into his tent to be his counsellor, for Clearchos was a man held in the highest honour by Cyrus and by the Greeks. Aeschines, the Greek orator, protests against his opponents calling in Demosthenes, his great rival, and says: "Why need you call Demosthenes to your support? To do so is to call in a rascally rhetorician to cheat the ears of the jury" (Against Ctesiphon 200). 