And Rabbi Yoḥanan said in the name of Rabbi Shimon ben Yehotzadak: "Any Torah scholar who does not avenge himself and bear a grudge like a snake when insulted is not considered a Torah scholar at all."

Really? But isn’t it written explicitly in the Torah: “You shall not take vengeance nor bear any grudge against the children of your people” (Leviticus 19:18)?

No problem there. That prohibition is written with regard to monetary matters and not personal insults, as it was taught elsewhere: "What is revenge and what is bearing a grudge? Revenge is when: One said to his fellow: Lend me your sickle, and he said: No. The next day he, said to the other : Lend me your ax. If he said to him: I will not lend to you, just as you did not lend to me, that is revenge.

And what is bearing a grudge? If one said to his fellow: Lend me your ax, and he said: No, and the next day he, said to the other: Lend me your robe; if the first one said to him: Here it is, as I am not like you, who would not lend to me, that is bearing a grudge."

But does the prohibition against vengeance really not also apply to matters of personal anguish suffered by someone? Wasn’t it taught elsewhere: "Those who are insulted but do not insult others, who hear themselves being shamed but do not respond, who act out of love for God, and who remain happy in their suffering, about them the verse states: 'May God's friends be as the sun rising in might' (Judges 5:31). So actually, the scholar may keep resentment in his heart, though he should not act on it."

There's another contradictory teaching: But didn’t Rava say: With regard to whoever forgoes his reckonings with others for injustices done to him, the heavenly court in turn forgoes punishment for all his sins? Maybe that's only when the offender has sought to appease him, in which case he should allow himself to be appeased. However, if no apology has been offered, the scholar should not forgive him, in order to uphold the honor of the Torah.