Matthew 20:9 - Ellicott's Commentary On The Whole Bible

Every man a penny. — The scale of payment rested on the law of a generous equity. The idleness of the labourers had been no fault of theirs, and the readiness with which they came at the eleventh hour implied that they would have come as readily had they been called at daybreak, and therefore they received a full day’s wages for their fraction of a day’s work. The standard of payment was qualitative, not quantitative. In the interpretation of the parable, the “penny,” as before, represents the eternal life of the kingdom of heaven. No true labourer could receive less; the longest life of labour could claim no more.