Bibliotheca Historica
Diodorus's universal history from mythological times to Caesar's Gallic War, cited via Justin for listing six ancient legislators with Moses first.
Preface and Praise of Sacred Scripture
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Moses as the Most Ancient Theologian, Philosopher, Poet, and Historian
— Cited via Justin: Diodorus lists six ancient legislators, Moses first
"Diodorus, the most esteemed of all historians... lists six ancient legislators, and first of all Moses"