Jesus was speaking to his disciples.
Many who are first will be last, and many who are last will be first.
The kingdom of heaven is likened to a man that is a homeowner, who went out early in the morning (probably 6am) to hire laborers to work in his vineyard. When he had agreed with the laborers for a penny a day, he sent them into his vineyard to work.
He went out about 9am and saw others standing idle in the marketplace.
Owner of the vineyard: You go also into the vineyard, and I will pay you whatever is right.
And they went to the vineyard to work.
The owner of the vineyard went out about noon and 3pm and did the same thing.
At about 5pm, he went out and found others standing idle.
Owner of the vineyard: Why do you stand here idle all day?
Those who stood idle: Because no man has hired us.
Owner of the vineyard: You go also into the vineyard, and you will receive whatever is right.
The lord of the vineyard (to his steward, when evening came): Call the laborers and give them their pay, beginning with the last ones hired and ending with those hired first.
When they that were hired about 5pm came, every man received a penny.
So when the ones hired first came, they thought that they should have received more; and they each received a penny also.
When they had received a penny, they murmured against the master of the house.
Those hired first: These last have worked only one hour, and you have made them equal to us, who have done most of the work and have labored during the heat of the day.
Owner of the vineyard (to one of them): Friend, I have done you no wrong. Didn’t you agree with me to work for a penny? Take what is yours and go your way. I will give to the last the same as I give to you. Is it not lawful for me to do what I will with my own money? Is your eye evil (envious or wishing evil on another), because I am good?
Jesus concluded: So the last shall be first, and the first last: for many be called, but few chosen.