32 • Before him will be gathered all the nations,
• and he will separate people one from another
as a shepherd separates the sheep from the goats.
33 • And he will place the sheep on his right,
but the goats on the left.
Well, how do you go about separating sheep from goats? We're not talking about classifying representative pictures of sheep and goats into order or arranging stuffed animals in a display, for although such a differentiation can be done quite 'scientifically' that task would be merely childsplay in spite of the obvious similarities between them.
If we try to separate sheep from goats on religious grounds we are in trouble for the opposite reason since both are kosher, parting the hoof and chewing the cud, and may be eaten by observant Jews accordingly, and when it came to sacrifice, a sheep and a goat were of roughly equivalent value, much as pigeons and turtledoves were.
The two main occasions where one kind was specified rather than another were when lambs were specified for Passover and goats for Yom Kippur, the Day of Atonement. Here we are getting closer to the idea of separation because on the original night of Passover, the lamb's blood was placed on the doorposts of the houses where the Passover was to be eaten to separate those inside from those outside the protection of the blood. On Yom Kippur the two goats were separated by lot (a good method to separate two goats but not sheep from goats) the one goat was for sacrifice to the LORD, the other (the proverbial 'scapegoat') was 'for Azazel,' and whatever happened to that goat when it was led into the wilderness, its blood was not shed.
The clue about how the sheep and the goats are to be separated lies in the text itself. We need to ask how does a shepherd separate sheep from goats? And the answer is given elsewhere by the 'Good Shepherd' himself:
So, for such is human nature, there will be many from all nations who will be wondering, since they can't be sure of being among the sheep simply by belonging to the right nation, what is it that marks them out as a sheep rather than as a goat? Both goats and sheep are headstrong and will go their own way but those who know the Shepherd's voice will hear his clear instruction, 'Go to the right.' and they will never perish.
My sheep hear my voice, and I know them, and they follow me. I give them eternal life, and they will never perish, and no one will snatch them out of my hand. My Father, who has given them to me, is greater than all, and no one is able to snatch them out of the Father's hand. [John 10:27-29]