The King will reply, "I tell you the truth, whatever you did for one of the least of these brothers of mine, you did for me."
The depth of this verse is hard to understand or explain. First, what an incredible thing for Jesus to call any of us brothers! But we know that he is not ashamed to call us family.
Both the one who makes men holy and those who are made holy are of the same family. So Jesus is not ashamed to call them brothers.
He has made us from enemies into family members, and I don't feel able to explain the depth of that other than to say what more amazing transformation could there be in a human relationship?
That we as Christians are brothers and sisters with Jesus isn't even the main point of this verse. He just mentions it as he is saying something else, and that something else is that when we do something for one of our brothers and sisters, that we do it for him.
This is the context of the verse:
When the Son of Man comes in his glory, and all the angels with him, he will sit on his throne with heavenly glory.
All the nations will be gathered before him, and he will separate the people one from another as a shepherd separates the sheep from he goats. He will put the sheep on his right and the goats on his left.
Then the King will say to those on his right, "Come, you who are blessed by my Father; take your inheritance, the kingdom prepared for you since the creation of the world.
For I was hungry and you gave me something to eat, I was thirsty and you gave me something to drink, I was a stranger and you invited me in, I needed clothes and you clothed me, I was sick and you looked after me, I was in prison and you came to visit me."
Then the righteous will answer him, "Lord, when did we see you hungry and feed you, or thirsty and give you something to drink? When did we see you a stranger and invite you in, or needing clothes and clothe you? When did we see you sick or in prison and go to visit you?
So the main point of the verse is that what we do for others, we do for Jesus. If you consider that for any amount of time, you will at least find it surprising and awe inspiring, and you may find it terrifying.
It's so surprising that Jesus prophecies that Christians will be surprised by it, even though now we know ahead of time that it will happen. We hear this story, and we can believe that it will come true one day, and yet we will still be surprised when the time comes.
One last thing is that it provides such a practical way to show our love for Christ. Do you have love for Christ? Are you grateful for what he has done for you? Do you wish you could express that joy and gratitude in a practical way?
Then serve your brothers and sisters in the way Jesus describes, and you will in fact be serving Jesus himself. It sounds crazy, and even after memorizing this and thinking about it quite a bit, I can't wrap my mind around it, but it's true.