The Agony in the Garden (Mark 14:32; Luke 22:40). The peculiar intensity of Christ's agony at Gethsemane presents a difficult problem. It cannot have been due to fear of death, for He came to Jerusalem expressly to die, and never faltered in His resolve, nor is the foreseen flight of the disciples, the treachery of Judas, the denial of Peter, and the sin of the Jewish nation in rejecting and crucifying Him, sufficient to account for it. Perhaps the explanation is to be found in the mystery of the Atonement. He was to bear the sins of the whole world, and the thought of that awful burden oppressed Him. 'The Lord felt the bitterness of death, He tasted it as the wages of sin; and this alone is the bitterness of death—not His own, but so much the profounder and keener as the sin of the whole world' (Dale).
The best commentary on Gethsemane is Hebrews 5:7. Important additional details are found in St. Luke's Gospel (Western text).