Since then we read that the Lord was sorrowful, let us discover the causes of His agony. He had forewarned them all that they would be offended, and Peter that he would thrice deny his Lord; and taking him and James and John, He began to be sorrowful. Therefore He was not sorrowful till He took them, but all His fear began after He had taken them; so that His agony was not for Himself, but for them whom He had taken.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: in loc.