Here's the third musical phrase:
In the first verse, the text here is "He helps us free from ev'ry need." "Ev'ry" is sung with a melisma (C B A), and that musical range gives a sense of the word's meaning.
The other things I noticed all pertain to the last musical phrase:
In the second verse, the text here is "He holds the field forever." "Forever" is sung with a melisma (A F E D C), musically giving something of a sense of this long period of time. Similarly, in the fourth verse, the text here is "The Kingdom ours remaineth," with "remaineth" sung to the same melisma and with the same musical impression.
In the third verse, the text here is "One little word can fell him" ("him" being "This world's prince"). There's a descent in the tune (spanning an octave) that musically illustrates that "fell[ing]." "Fell" is even sung with a melisma (F E D), emphasizing the descent.
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*In the hymnal, the tune is listed as just "Ein feste Burg," but in German, Burg is a feminine noun, so it takes a feminine article: die (definite) or eine (indefinite). I have Bach's cantata based on the tune, and the CD case has the title printed correctly ("Ein' feste Burg"), as does the notation I downloaded from IMSLP (which is apparently from 1870):
Unfortunately, it seems that the apostrophe at the end of "ein'" is often omitted.
