Narratives and similes are not the only literary techniques that populate the pages of the four Gospels. Many brilliant metaphors, though few in number when compared to the similes, used not in its original sense but a transferred sense are found in the Gospels. Matthew makes use of a metaphor in the address of John the Baptist to the Pharisees and so does Luke. “You snakes!” (Mt. 3:7, Lk. 3:7) The meanness of the Pharisees is compared to the evilness in snakes who were ‘biting people unawares, killing not for the sake of food but for the sake of doing harm.’
In The Gospel of Mark, he uses the metaphor of yeast.
“Look out,” Jesus warned them, “And be on your guard against the yeast of the Pharisees and the years of Herod” (Mk. 8:15).
Mark in this profound metaphor explains the function of yeast and then draws the underlying meaning. Yeast has the power of slowly infiltrating and permeating the dough into which it is put. The influence of the pharisees, their legalism and of Herod Antipas, his materialism and religious indifference might also affect the apostles. so Jesus warns them against their influence as if it were yeast.
John’s metaphor of ‘a slave of sin’ deserves some attention. Jesus answered to them, “Verily, Verily, I say unto you, whosoever commiteth sin is the servant of sin.” John in chapter eight uses this metaphor to show the true nature of moral slavery in order to bring out the true nature of freedom.