suru verb (special), intransitive verb
Intransitive: to exert effort, often in a sustained or arduous way. Somewhat formal or literary.
彼は国のために労することを誇りに思っている。
He takes pride in laboring for his country.
suru verb (special), transitive verb
put to work; make work
Transitive: to cause someone to work, often implying hardship or exploitation. Less common than the intransitive sense.
昔の工場主は労働者を過酷に労した。
Factory owners in the past made workers labor harshly.