John Milton was a Puritan who supported Oliver Cromwell's republican commonwealth after the execution of King Charles I of England. During this period, politics and religion were tied closely together, so that being "useful" to the government meant being "useful" to God, at least for Milton. The poem displays Milton's encyclopedic knowledge of the Bible but also his reforming instincts. Milton is not afraid to challenge the supposed moral of the New Testament "Parable of the Talents" by pointing out the difference between God and the lord from the story. The sonnet gives expression to intense religious emotions, but its rational and rhetorical qualities are equally important.
Patience contrasts God as "king" with the lord from the "Parable of the Talents." If God were really like the lord in the parable, He would be profiting from humanity.
The poem argues that God will eventually reveal a person's vocation without her having to actively search for it.