Charles Ellicott Commentary Exodus 19:22

"And let the priests also, that come near to Jehovah, sanctify themselves, lest Jehovah break forth upon them." — Exodus 19:22 (ASV)

The priests. — This has been called an anachronism, since the Levitical priesthood was not yet instituted. But the Israelites, like all other ancient tribes or races, must have had priests long before this, appointed on one principle or another. It is a reasonable conjecture that previously the heads of families had exercised sacerdotal functions.

Break forth — that is, punish in some open and manifest way. Compare the “breach” upon Uzzah (2 Samuel 6:8).