The third verse ends with the line "To all the world Your grace extend." "Grace" is sung with a melisma (G B), so there's a musical sense of its being "extend[ed]." To some degree, there's a sense of this "extend[ing]" even in just the note values, since they increase from quarter notes to a half note and then to a whole note.
While looking over the hymn again, I noticed a cross inscription in the third musical phrase:
This corresponds to the text in the third verse, which is "You take the whole world's sin away." Christ's crucifixion was the means by which this was effected.
