If a separate scripture or wholly new legislation is imposed as an essential condition, one must account for figures who conveyed or upheld an earlier law. Some scriptural cases place a messenger's mission within an already-established legal tradition.
An essential condition must exist in every valid instance; a frequent attribute may be common without being universal. Treating the latter as the former makes a definition too narrow.
Technical definitions must therefore be assessed against relevant examples and counterexamples. The decisive religious claim is divine appointment, not simply conformity to one proposed taxonomy.