This little poem comes from the distichs of Publius Faustus Andrelinus (c. 1460-1518). You can find his hecatodistichon, his "hundred distichs," at Google Books.
Pax
Securus placida mundus sub pace quiescit:
Tranquillum est summi pax opus alta dei.
The vocabulary is keyed to the DCC Latin Vocabulary list. There are only two words in this poem that are not on the DCC list:
placidus -a -um: quiet, calm, gentle, kindly
tranquillus -a -um - calm, quiet, tranquil
altus -a -um: high, lofty; deep
deus -ī m.; dea -ae f. god; goddess
mundus -ī m.: world, universe, heavens
opus operis n.: work
pāx pācis f.: peace
quiēscō quiēscere quiēvī quiētum: keep quiet; sleep
sēcūrus -ā -um: free from care, tranquil; careless
sub: under, close to (+acc. or abl.)
sum, esse, fuī: be, exist
summus -a -um: highest, farthest, last