A.T. Robertson Commentary Matthew 25:40

"And the King shall answer and say unto them, Verily I say unto you, Inasmuch as ye did it unto one of these my brethren, [even] these least, ye did it unto me." — Matthew 25:40 (ASV)

Ye did it unto me (εμο εποιησατε). Dative of personal interest. Christ identifies himself with the needy and the suffering. This conduct is proof of possession of love for Christ and likeness to him.