Jesus used this term on several occasions and in slightly different ways.

Matt. 19:30: “But many who are first will be last, and the last first.”

This is also recorded in Mark 10:31: “But many who are first will be last, and the last first.”

Luke 13:29-30: “They will come from the east and the west, from the north and the south, and sit down in the kingdom of God. “And indeed there are last who will be first, and there are first who will be last.”

In these particular statements Jesus is referring to the Jews who were called first by God, whom He came to first will not all be first but last. The Gentiles who believe in Him will enter the kingdom before they because they were willing to follow and serve.

Jesus defines the concept of being first: Matt. 20:27-28: “And whoever desires to be first among you, let him be your slave-- “just as the Son of Man did not come to be served, but to serve, and to give His life a ransom for many.”

This is also recorded in Mark 10:44-45 “And whoever of you desires to be first shall be slave of all. “For even the Son of Man did not come to be served, but to serve, and to give His life a ransom for many.”

Mark 9:35 And He sat down, called the twelve, and said to them, “If anyone desires to be first, he shall be last of all and servant of all.”

There are principles Jesus taught on - servanthood.

Luke 22:25-27: And He said to them, “The kings of the Gentiles exercise lordship over them, and those who exercise authority over them are called 'benefactors.' “But not so among you; on the contrary, he who is greatest among you, let him be as the younger, and he who governs as he who serves. “For who is greater, he who sits at the table, or he who serves? Is it not he who sits at the table? Yet I am among you as the One who serves.”

We are to follow Jesus’ example. If we walk in the Spirit we will not think highly of ourselves and are willing to serve others, no matter who they are. This is the opposite of how the world works were if one wants to be great they make themselves great at the expense of others.

After the tribulation is ended by Jesus’ return, he divides the sheep from the goats and those who served the brethren in unfortunate circumstance s ask 'When did we see You a stranger and take You in, or naked and clothe You? 'Or when did we see You sick, or in prison, and come to You?' “And the King will answer and say to them, 'Assuredly, I say to you, inasmuch as you did it to one of the least of these My brethren, you did it to Me.' (Matt. 25:38-40).

Again, servanthood is rewarded by Jesus. A servant does things without any credit, they would do the same whether they are acknowledged or not. They do it because they are committed to the master, willing to serve, not just because it is their duty but because of their love.

In Luke 7:28: “For I say to you, among those born of women there is not a greater prophet than John the Baptist; but he who is least in the kingdom of God is greater than he.” John happened to be the greatest of the Old Testament prophets. He ministered in the transition period as he was the one privileged to introduce Israel’s Messiah to the people. Yet Jesus says everyone who serves will be greater than John.

Look at Paul’s attitude, as an apostle he says: “For I am the least of the apostles, who am not worthy to be called an apostle, because I persecuted the church of God.”(1 Cor.15:9).

If one humbles himself and is willing to be a servant to others they will be considered great in the kingdom. The more they serve the more rewards there will later be for them.