This is a reference to the parable of the Workers in the Vineyard, found in Matthew 20:1-16.
So the last shall be first, and the first last: for many be called, but few chosen
It is the story of a vineyard owner who hires different groups of casual labourers for different lengths of time. At the end of the day, the landowner pays them all equally, starting payments with the last person to get there. It's a story of equality and generosity, but also of entitlement because the ones who had been there longer thought they were entitled to more.