John Wesley on Matthew 20:1

That some of those who were first called may yet be last, our Lord confirms by the following parable: of which the primary scope is, to show, That many of the Jews would be rejected, and many of the Gentiles accepted; the secondary, That of the Gentiles, many who were first converted would be last and lowest in the kingdom of glory; and many of those who were last converted would be first, and highest therein. The kingdom of heaven is like - That is, the manner of God's proceeding in his kingdom resembles that of a householder. In the morning - At six, called by the Romans and Jews, the first hour. From thence reckoning on to the evening, they called nine, the third hour; twelve, the sixth; three in the afternoon, the ninth; and five, the eleventh. To hire labourers into his vineyard - All who profess to be Christians are in this sense labourers, and are supposed during their life to be working in God's vineyard.