Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 14:17-21

“But the other disciples began to be saddened on account of the word of the Lord; for although they were free from this passion, yet they trust Him who knows all hearts, rather than themselves. It goes on: And he answered and said unto them, It is one of the twelve, that dippeth with me in the dish.”