work, Pirkei Avot

O sages, be careful with your words;
For you may incur the penalty of exile,
and be banished to a place of evil waters;
The disciples who come after you
will drink of them and die,
and the name of Heaven be profaned.
—Avtalion

Take care in studying,
for error in study
is as serious as intentional sin.
—Rabbi Yehudah