Deuteronomy 1:3

In the fortieth year, in the eleventh month, on the first day of the month, Moses spoke to the children of Israel, according to all that the Lord had commanded him to give to them.
Deuteronomy 1:3 Modern English Version (MEV)
 
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And it came to pass in the fortieth year,.... That is, of the coming of the children of Israel out of Egypt:
 
in the eleventh month; the month Shebet, as the Targum of Jonathan, which answers to part of January and part of February:
 
in the first day of the month, that Moses spoke unto the children of Israel according to all that the Lord had given him in commandment unto them; repeated to them the several commandments, which the Lord had delivered to him at different times.
 
John Gill’s Exposition of the Bible
 
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The number “40” is used throughout the Bible, often associated with the wilderness, and is used to express a large number, whether years, days, or whatever unit of measure is being discussed. Whenever it was used, it would remind the children of Israel of the many years they spent wandering in the wilderness as it was an integral memory of their national psyche.