The hills are verdured pasture-wise;
The angel hosts with freshness go,
And seek with laughter what to brave;—
And binding all is the hushed snow
Of the far-distant breaking wave.
And from a cliff-top is proclaimed
The gathering of the souls for birth,
The trial by existence named,
The obscuration upon earth.
And the slant spirits trooping by
In streams and cross- and counter-streams
Can but give ear to that sweet cry
For its suggestion of what dreams!
And the more loitering are turned
To view once more the sacrifice
Of those who for some good discerned
Another sly allusion, this time to Hamlet’s  “To be or not to be” speech,  which soberly contemplates life after death: 
 ….To die, to sleep; To sleep: perchance to dream: ay, there’s the rub; For in that sleep of death what dreams may come When we have shuffled off this mortal coil, Must give us pause. 
 Frost flips this trope on its head by having the souls in paradise joyfully imagine “what dreams” may come once they return to life from the afterlife.
The Trial by Existence