Bamidbar 4:19-21

Orthodox Jewish Bible

¹⁹ But this do unto them, that they may live, and not die, when they approach unto kodesh hakodashim (the most holy things): Aharon and his banim shall go in, and appoint them every one to his avodah (service, ministry) and to his massa (burden);

²⁰ But they shall not go in to look for a single instant at hakodesh, lest they die.

[NASO]

²¹ And Hashem spoke unto Moshe, saying,