Let us answer them in the follow ways:
1. What do we confess? What saith the Scripture?
WCF Chapter 33: Of the Last Judgment
33:1 God hath appointed a day, wherein He will judge the world in righteousness, by Jesus Christ,1 to whom all power and judgment is given of the Father.2 In which day, not only the apostate angels shall be judged,3 but likewise all persons that have lived upon earth shall appear before the tribunal of Christ, to give an account of their thoughts, words, and deeds; and to receive according to what they have done in the body, whether good or evil.4
1) Act.17:31. 2) Jn.5:22,27. 3) 1Cor.6:3; 2Pet.2:4; Jde.1:6. 4) Ecc.12:14; Mt.12:36,37; Rom.2:16; 14:10,12; 2Cor.5:10.
There will certainly be a judgment that reckons with works. The question is: are works the
basis for eternal life? Mt.25:31ff doesn't say that, only that the destiny of each group is consistent with the imputed value of such works as they performed. The "for..." (γαρ) in vv35 & 42 is an extremely common and versatile copulative, and testifies to a relation between the statements before and after, but does not promise causation, or any proof of "order" to this relation. Given the nature of things, what each was (sheep or goat) preceded all their activity as sheep or goat. Their work did not make them a sheep or a goat. The separation did not make them either. The kingdom was prepared for them (specific) before the foundation of the world, certainly before anything they had done.
2. Who is focused on
works in the passage?
Remember first, the nations are not separated because of what they've done, but because of who they are: Sheep and Goats.
The King (the Son of Man) welcomes the sheep on his favorable hand, and "thanks" or "approves" them regarding their solicitude on his behalf, which is basically the same as recognizing their love for him who invites them in. Interestingly, the sheep seem somewhat taken aback by the King's comments. "Works, Lord? What works?" they seem to say. They must be reminded of their thoughtless love that wrought this pleasure in him. Apparently, they also took no thought for this future commendation at the time they were loving the Lord's brethren. It isn't as if they were doing the work out of any expectation of reward: kingdom and eternal life as opposed to fire and everlasting punishment.
The Goats, on the unfavorable left hand, are cursed and dispatched--once again, because they are goats, and on the left; and not because they failed at working, though they did fail at working. But again, interestingly, they seem shocked and taken aback at the harsh judgment respecting their works. "Works? O LORD!
when did we not work for you?" It was their lack of love for those whom the Lord loved that he censures. Whatever they might have done for their own brethren may have been very important to them; such work, if done, may have even led them to think they should someday be rewarded. But the Lord counts everything they did as nothing, and everything they did not (for the least of "these") as personal despite.
So in the end, those who have works don't need them. And those who think they have them have nothing.