Real Bible Translation - Matthew 25:41

At that time he will say also to those from out of good-named/disguised ones, 'Traverse across away from myself, those who have been damned into the Eternal (aiōn) Sacrificial Fire, the one which has been prepared by the Accuser and the Angels of Himself.'^47b

Julia Smith Literal 1876 Translation:
Then shall he say to them from the left, Go away from me, the cursed, into eternal fire, prepared for the devil and his messengers:

LITV Translation:
Then He will also say to those on His left, Go away from Me, cursed ones, into the everlasting fire having been prepared for the Devil and his angels.

Footnotes

47b

The preposition ὑπό + genitive is the more usual, and explicit way in which agency is expressed:

ἡτοίμασται ὑπὸ τοῦ Πατρός

"prepared under/by the Father" (Matt. 20:23)

However, this is not the rule, and especially with the perfect passive tense it often expresses agency.

Smyth §1488: Dative of the Agent

The dative of agent with a perfect passive is a well-established usage in classical and Koine Greek. Used especially with:

1. Perfect and pluperfect passives, and
2. Verbal adjectives in -τός and -τέος.

Importantly, Smyth notes:

“The notion of agency does not belong to the dative, but it is a natural inference that the person interested is the agent.”

So the core idea is that the dative expresses the person concerned / interested, and from that concern, agency may be inferred — hence the ambiguity.

Examples:

ἐμοὶ καὶ τούτοις πέπρα_κται → “it has been done by me and these men” (D. 19.205).
τοσαῦτά μοι εἰρήσθω → “let so much have been said by me” (L. 24.4).
ἐψηφίσθαι τῇ βουλῇ → “let it have been decreed by the senate” (inscr.).

These are exactly parallel to τὸ ἡτοιμασμένον τῷ διαβόλῳ — so it can be “prepared by the accuser/devil” if the devil is construed as the interested/acting party.

BDF §1186

BDF states that the dative sometimes denotes the agent with the perfect and pluperfect passive, rarely with other passive tenses.
Examples:
- ἐξετάσαι τί πέπρακται τοῖς ἄλλοις → “what has been done by the others.”
- ἐπειδὴ αὐτοῖς παρεσκευάστο → “when preparation had been made by them.”
- πολλαὶ θεραπείαι τοῖς ἰατροῖς εὑρήνται → “many cures have been discovered by physicians.”

Matthew 25:41:

ἡτοιμασμένον τῷ διαβόλῳ
- As dative of interest: “prepared for the devil.”
- As dative of agent (in Smyth’s sense): “prepared by the devil.”

Thus both readings are grammatically defensible. The decisive factor is context and usage preference:

NT Greek usually leans toward “for” (dative of advantage/disadvantage) in such constructions.
But grammarians (Smyth §1488, BDF §1186, §1187) confirm the agentive possibility is not only theoretically possible but attested.

(cf. Smyth §1488 - dative of the agent, esp. perfects/passives and BDF §1186, §1187)