“EMPLOYEES MUST WASH HANDS BEFORE RETURNING TO WORK”

This is a classic MAD Magazine cartoon (drawn in their signature grotesque style, mocking workplace hygiene rules in the most literal, disgusting way possible.
The joke is built around the sign that says:
“EMPLOYEES MUST WASH HANDS BEFORE RETURNING TO WORK”
The pompous, snooty restaurant manager (the tall thin guy in the red jacket and bow-tie) takes the sign completely literally and forces the janitor to wash his own (the manager’s) hands for him, instead of the janitor washing his own hands.
The sequence of panels shows how far the janitor goes to obey the instruction:

The manager stands at the sink holding out his hands expectantly.
The manager gets angry when the janitor doesn’t immediately understand.
The janitor pees at the urinal.
The janitor vomits into the toilet.
The janitor finally washes the manager’s hands with soap.
The manager smugly points at the sign to justify himself.
The manager walks out, leaving the janitor to clean up the overflowing trash, spilled mop bucket, and general filth he just created… without ever having washed his own hands.

It’s a deliberately revolting satire on:

Lazy, hypocritical bosses who interpret rules only when it benefits them.
Literal-minded over obedience to signs.
The absurdity of making the lowest-paid worker do the most disgusting jobs while the manager does nothing useful.

Typical MAD Magazine bathroom humor: gross, exaggerated, and sharply critical of authority.