Jesus tells us there will be a day when all the nations will gather before Him and He will separate us one from another as a shepherd separates the sheep from the goats. The sheep will be put on His right and the goats on His left.
He says He will tell those on the right that they are blessed by His Father and will offer them their inheritance in the kingdom which has been prepared since the creation of the world.
The Lord describes the sheep (and later contrasts them with the goats). The sheep are those who fed Him when He was hungry, gave Him something to drink when thirsty, visited Him in prison, clothed Him, and cared for Him when He was sick.
Today I think He might add, "I was in the womb and you protected Me."
Jesus then promises, "The King will say, 'I tell you the truth, whatever you did for one of the least of these brothers and sisters of mine, you did for me.'"
For the full reference, read Matthew 25:31-46.