To simply state that the Bible has had one - and only one - understanding (in a theological sense) of goats and sheep would be disingenuous. But, in the gospels, Christ gives us a better - more full - understanding.
Let’s take a few moments to walk through the Old & New Testaments to see how goats and sheep are portrayed.
Old Testament Sheep & Goats in History
We see all the way back even in Genesis (32:14) that both were acceptable sacrifices to atone for sins. That is reiterated in the rest of the Pentateuch.
Both were acceptable animals to eat, being clean animals. The sheep, or ram, is often shown to be the “go to” sacrificial animal though - as seen in the Passover, or Paschal, Lamb. Yet, in the Day of Atonement, there are two goats used for this special sacrificial day. One goat is slaughtered, representing that sins are covered by the blood of another. The other goat has the sins of the people of God “laid on it” by the high priest … and then sent out into the wilderness. The thought is that their sins are sent outside the camp, the dwelling place of God and His people, never to return!
It can be noted here, that when goats and sheep are depicted… they are both sacrificial. They are then both q foreshadowing to the Perfect Sacrifice of Christ for His people. This whole system was fulfilled by Christ in His coming, in His sacrifice. It was perfectly, and eternally, accepted in His resurrection.
Old Testament Sheep & Goats in Poetry & Prophesy
When we transition out of the historical narrative of God’s people, we see more allegory and analogy. Psalm 23 is a good example - under God (Christ) as our Great Shepherd we are taken care of. We are given perfect food, and given life-sustaining water (not unlike Christ’s body and blood). The Psalms are full of examples where the people of God are described like sheep in different circumstances. Whether being led, being slaughtered, being lost or found… we see this concept of God’s people being represented by a flock of sheep.
I’m fact, looking for examples of “goat” used in the Old Testament, following the historical narrative section, there really aren’t any meaningful examples. There are examples of sacrifice (in Isaiah for instance), or prophetic connections to historical rulers (like in Daniel). But nothing that seems to connect God’s people to goats.
In fact, you could argue that Ezekiel 34:17 begins to show a shift in the Biblical understanding of “theological” sheep and goats. Here we read that God is very displeased with His worldly under-shepherds. They have failed in their calling and duty. The flocks have scattered and these men will be punished. The scattered flocks have gone far away from their homes, and the LORD now will be in charge of bringing them back. God Himself will be the Rescuer.
“I will seek the lost, bring back the strays, bandage the injured, and strengthen the weak, but I will destroy the fat and the strong. I will shepherd them with justice.”
Ezekiel 34:16 CSB
The LORD then goes on to declare that He will judge, and separate, those who call themselves by His name.
“As for you, my flock, the Lord God says this: Look, I am going to judge between one sheep and another, between the rams and goats.”
Ezekiel 34:17 CSB
The LORD is saying there is a justifiable difference between those people who He would consider to be sheep and goats. There has been an infiltration in the flock… one could say that wheats and tares are intermingled into the same area. God will separate these two “flocks.” The rams (sheep) from the goats.
New Testament Sheep & Goats
Our main text is Christ’s words in Matthew 25:31-33:
“When the Son of Man comes in his glory, and all the angels with him, then he will sit on his glorious throne. All the nations will be gathered before him, and he will separate them one from another, just as a shepherd separates the sheep from the goats. He will put the sheep on his right and the goats on the left.”
Matthew 25:31-33 CSB
Very reminiscent of Ezekiel, our LORD recognizes that the flock has been intermixed. People who say they follow Christ have (and will continue to until the end of time) hidden themselves among the flock of God. They speak the same words. They may even do or say incredible things (Matthew 7:21-23). But God knows who is His own. And they will be judged accordingly.
So what differentiates the sheep from the goat? We see it in the following verses of Matthew 35, and then reiterated throughout the New Testament:
“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 took me in; I was naked and you clothed me; I was sick and you took care of me; I was in prison and you visited me.’ … “And the King will answer them, ‘Truly I tell you, whatever you did for one of the least of these brothers and sisters of mine, you did for me.’”
Matthew 25:35-36, 40 CSB
The sheep are known by their obedience to God. They have “worked out their own salvation with fear and trembling…” (Philippians 2:12). They are known by their love (John 13:35). They have born fruit (Galatians 5:22) and put on Christ (Colossians 3:12-17). And all of this has been “accomplished” because it is “God working in [us] both to will and to work according to His good purpose” (Philippians 2:13).
The sheep and the goats represent, in Christ’s Words (connecting to Ezekiel), a separation in kind. Sheep and goats are very similar. Their coats are similar. They both have capacity to give milk. Both, under the old covenant, were acceptable sacrifices. They even have very similar physical looks. But eschatologically (concerning the end times) they are wholly different.
One is chosen by God, in Christ, by the indwelling of the Holy Spirit to be brought into the Sheep-Fold of God. The other will be “passed over” and separated to be cast into eternal punishment. Their sinful actions are paid for, eternally, just not by the blood of Christ. All sin will be paid for… either by us in the eternal wrath of God, or by Christ’s infinitely worthy (and accepted) sacrifice.
The how and why as to God’s choice is both a mystery and a revealed Truth. He alone is worthy of making such decisions, and we - as the clay - are not always privy to the inner workings of a divinely eternal God. But, we can rest assured that if we place our full trust in Christ - a faith given in grace - our actions will progressively begin to reflect that change in priorities. Maybe not immediately… and definitely more and more over our life time… but ultimately we who are grounded in Christ (justified by His work on the cross) will be sanctified (made more in His image in this lifetime) and glorified in the last days.
At that time we will be separated off, having followed in Christ’s likeness, empowered by God to care for “the least of these” … showing that He is our supreme love - with all thanks and honor to Him alone! Amen!