The two seven-letter words that answer this flat differ by only one letter - but the letters are not consecutive. (An "s" is added to the second word and is exempt from the clue.)

Moses gathered up his _ _ _ _ _ _ _,
And neared the mighty foe.
He then put forth those well-known
   words,
"Let my people go."

(Ten awful _ _ _ _ _ _ _ s did Egypt see
Before the Israelites were free.)

Answer:

COURAGE - SCOURGEs

Credit:
The Enigma 
June, 2020
A. CHEMEM