In his speech On Imperial Rule (or On Monarchy), Synesius of Cyrene offers some advise to the emperor Arcadius (r.395-408). More information about this speech, together with a brief summary, can be found here.
Throughout this speech, the word "Scythians" refers to the Tervingian Germans (who would later be known as Visigoths), whereas "king" refers to emperor.
The text is offered here in the translation by A. Fitzgerald. The four-digit numbers are page numbers of the Migne edition.
On Imperial Rule 17
  The institution of embassies, sacred as it is in other respects, is in this connection of the highest value. Conferring with these, the king will know that which is afar no less than that which is near, nor will foresight for his kingdom be bounded by the sense of sight. He can even raise up that which is fallen, though he see it not, can give largess to races in distress, and remit state burdens to such persons as have long been groaning under them. He will break off a war that threatens, and will terminate a war which has broken out, and will adjust everything else in time, for by the agency of embassies he will be able, like the god, 'to see and hear everything'.note
 To these let him be accessible, and 'gentle as a father',note whether they come from near or from afar, for so I have heard Homer speaking once for all of the king that is at peace with himself.