Acts 7:30

And when forty years were expired,— This circumstance might have been handed down by tradition, or received by immediate inspiration, as the express time of Moses's continuance in voluntary exile isnot mentioned in the Old Testament; and no doubt many other circumstances respecting that great legislator, which are not related in that concise history, were handed down either by tradition or by some writings then extant. Respecting the subsequent circumstances, we refer the reader to the notes on Exodus 3.