The ruler (prince) of this world" refers to Satan. Jesus was constantly aware of Satan's hostile presence and was preparing for his last attack. Satan first afflicted Jesus at his temptation (Mt 4:1-11; Mk 1:12; Lk 4:1-13). Luke, however, indicates that there would be other times when the devil would tempt Jesus - Luke 4:13 NKJV Now when the devil had ended every temptation, he departed from Him until an opportune time.