At times, Jesus was more demanding than Torah. In prohibiting divorce, for example, he went beyond Deuteronomy, which explicitly allows for divorce. From the mitzvah "You shall not murder," he concluded that one should not be angry with others since anger can lead to killing. From the mitzvah "You shall not commit adultery," he concluded that just glancing lustfully at a married woman is tantamount to adultery. Like a true hasid, Kesis was extreme in his ethical demands.
— Daniel Matt, Jesus through Jewish Eyes by Beatrice Bruteau, editor