ORIGEN: After the disciples celebrated the feast with their teacher and received the bread of blessing and ate the body of the Word and drank the cup of thanksgiving, Christ taught them to sing a hymn to the Father for these gifts and to pass from one height to another height, for the faithful are never able to do anything in the valley. So they went up to “the Mount of Olives,” where each one of them, like a fruitful olive tree, was able to say, “I am like a green olive tree in the house of God.” And those who had not yet become “like a green olive tree in the house of God” but were still “like olive shoots around the table” of their spiritual father, were also able to be present on the Mount of Olives, about which Zechariah prophesied. And how fitting it was that this mount of mercy be chosen as the place where the disciples would be forewarned of their future weakness. It is fitting because Christ did not wish upon them what he only foretold, for he was then already preparing to receive converts, not to banish defectors.
SAINT JOHN CHRYSOSTOM: “And when they had sung an hymn, they went out unto the Mount of Olives.” Let them hear this, as many as, like swine eating at random, rudely spurn the natural table, and rise up in drunkenness, whereas it were meet to give thanks, and end with an hymn
Hear this, as many as wait not again for the last prayer of the mysteries, for this is a symbol of that. He gave thanks before He gave it to His disciples, that we also may give thanks. He gave thanks, and sang a hymn after the giving, that we also may do this same thing.
But for what reason doth He go forth unto the mountain? Making Himself manifest, that He may be taken, in order not to seem to hide himself. For He hastened to go to the place which was also known to Judas.