an authoritative rule handed down by a ruler: a royal decree, or the settled law of a kingdom
This is a foreign word that entered Hebrew from Persian, and it belongs almost entirely to the world of the Persian court. Nearly every time it appears, in the book of Esther and once in Ezra, it names something the king puts in force: an order written up, sealed, and sent out to the provinces, or the fixed body of law and custom by which the empire runs.
The two shades sit close together and often blur. Sometimes the word points to one particular command issued for one occasion, such as the edict to destroy the Jews or the counter-edict that saves them. Sometimes it points to the standing law itself, the rules of Persia and Media that famously cannot be revoked, or simply the accepted way a thing is done. What holds the senses together is authority from the top: whatever a ruler lays down, whether once or for good, carries the weight of law.
Because it is a court word, it does not carry the moral or covenant flavor of the usual Hebrew words for God's law. It describes how a human empire governs. The one possible exception lies far outside Esther, in a single difficult line of Deuteronomy, where the reading itself is uncertain.
Nuances
Whether the consonants אשׁדת at Deuteronomy 33:2 actually contain the word דָּת ("law"), and if so what the phrase means, is a long-standing text-critical problem.
- contestedDivide the consonants as אֵשׁ דָּת, "fiery law" or "fire of the law," reading דָּת here as "law" and linking the line to the giving of the law at Sinai; the traditional reading behind the Masoretic accentuation and older versions.; BDB, s.v. דָּת
- contestedThe consonantal text is corrupt and does not contain דָּת; the line is re-divided or emended (for example to yield a geographical term or a reading closer to what the ancient versions reflect), so the word should not be counted here at all.; Jeffrey H. Tigay, Deuteronomy (JPS Torah Commentary), 1996