20. For--Greek, as in Eph 6:19, "On behalf of which."
      an ambassador in bonds--a paradox. Ambassadors were held inviolable by the law of nations, and could not, without outrage to every sacred right, be put in chains. Yet Christ's "ambassador is in a chain!" The Greek is singular. The Romans used to bind a prisoner to a soldier by a single chain, in a kind of free custody. So Ac 28:16, 20, "I am bound with this chain." The term, "bonds" (plural), on the other hand, is used when the prisoner's hands or feet were bound together (Ac 26:29); compare Ac 12:6, where the plural marks the distinction. The singular is only used of the particular kind of custody described above; an undesigned coincidence [PALEY].

JFB.