'Be strong and of a good courage' is phrased as an instruction, not a wish. Resolve here gets treated as something that can be commanded and chosen, not just something people either have or don't.
Practical & Devotionalלא ירפך means He will give you no looseness that you should be abandoned by Him (cf. Rashi on Deuteronomy 4:31).
Historical CommentatorsSelect a line on the left to view commentary.