I found this poem in the collection Philosophia Patrum edited by Julius Wegeler.
Mors Atra
Ah, homo si sciret, quando mors atra veniret,
Non sic dormiret, sed caeli regna sitiret.
The vocabulary is keyed to the DCC Latin Vocabulary list. There are two words in this poem that are not on the DCC list:
āter, ātra, ātrum: dark, black, gloomy
sitiō, sitīre: thirst, be thirsty, thirst for
caelum -ī n.: sky, heavens
dormiō -īre: sleep
homo hominis m.: human being
mors mortis f.: death
nōn: not
quandō: when?; since; si quando: if ever
rēgnum -ī n.: kingship, kingdom
sciō -īre -īvī/-iī -ītum: know
sed: but
sī: if
sīc: in this manner, thus; sīc . . . ut: in the same way as
veniō venīre vēnī ventum: come