Go with God.
Que vaya con Dios = (I hope that) you go with God. But if you're wanting to say it as a command, it would be:
Vaya con Dios - formal; Ve con Dios - informal.
Freddy Fender said it pretty good a long time ago.
In English it is " Goodbye" Old English , " God be with Ye "
Ray, "God be with ye" is late Middle English. That sentence in Old English is:
God þē mid sīe
Which literally is "God you with may-be". The word "þē" is "you" in accusative or dative, and the letter thorn (þ) is read as "th". "Mid" is like "mit" (with) in German, and "sīe" is the present subjunctive (yes, true and fully conjugated subjunctive) of "bēon" (to be), like in modern Spanish (but with the verb at the end, like in German) "Dios esté contigo".
But if you're wanting to say it as a command (which, to me, would be rather odd),
Do you also find "Go in peace." / "Go to the Devil." / "Go to h*ell." (all commands) odd?