This reading is from the regular Torah portion for this week, VaYelech. The Torah portion for the first day of Rosh Hashanah is Genesis 21:1-34.
And Moses called unto Joshua, and said unto him in the sight of all Israel: "Be strong and of good courage; for thou shalt go with this people into the land which HaShem hath sworn unto their fathers to give them; and thou shalt cause them to inherit it. And HaShem, He it is that doth go before thee; He will be with thee, He will not fail thee, neither forsake thee; fear not, neither be dismayed."
And Moses wrote this law, and delivered it unto the priests the sons of Levi, that bore the ark of the covenant of HaShem, and unto all the elders of Israel.