הוכח תוכיח את עמיתך

Thou shalt not hate thy brother in thy heart; thou shalt surely rebuke thy neighbour, and not bear sin because of him.

Rabbi Shimon ben Elazar would say in the name of Rabbi Meir: Do not try to make your friend feel better when he is still angry. [And do not attempt to comfort him when he is still in mourning. And do not ask him if he wants something when he has taken a vow not to have it.] And do not come to his house to try to see him on the day of his festival. (And some say:) If you have friends, some of whom challenge you and some of whom praise you, love the ones who challenge you and hate the ones who praise you. For those who challenge you are bringing you into the World to Come, and those who praise you are taking you out of the world.

He would also say: Anywhere a person goes, his heart goes. Where he stays, his heart stays. When he is settled, those around him feel settled. He would also say: Anyone who commits himself to studying words of Torah becomes surrounded by a circle of committed colleagues. And anyone who neglects studying words of Torah becomes surrounded by a circle of neglectful companions. And then he is attacked by a lion, a wolf, a tiger, a hyena, or a snake. Or soldiers or thieves come and surround him and take his money, as it says (Psalms 58:12), “For there is a God who judges upon the earth.” Shaul (ben Nanas) came and said: (There are) [four types of Torah scholars. (You) have] one who teaches himself but does not teach others, one who teaches others but does not teach himself, one who teaches himself and others, and one who teaches neither himself nor others.
The one who teaches himself but does not teach others – what is he like? He studies a chapter, or two or three, but he does not teach them to anyone else. He reviews them, and makes sure he does not forget them. This is the one who teaches himself but does not teach others.
The one who teaches others but does not teach himself – what is he like? He studies a whole section, or two or three, and then he teaches them to others. But he does not review them himself, and he forgets them. This is the one who teaches others but not himself.
The one who teaches himself and others – what is he like? He learns a whole section, to two or three, and then he teaches them to others. Then he reviews them, making sure he does not forget them, until he has them completely mastered. This is the one who teaches himself and others.
The one who teaches neither himself nor others – what is he like? He studies a whole section, or two or three. But he does not teach them to others, and does not review them himself, and eventually he forgets them. This is the one who teaches neither himself nor others.

Rabbi Hananya ben Ya'akov would say: When someone is up late at night learning words of Torah, this is a good sign. When someone is up late at night chatting, this is a bad sign.
Rabbi Ya'akov ben Hananya would say: When someone stays up late at night, and never speaks a word of Torah, it would be good and proper if his mother’s umbilical cord had been pulled back and he had never come out into the air and seen this world. Rabbi Elazar HaKappar would say: Anyone who respects his friends only for their money, in the end will be sent away from them in disgrace. And anyone who disgraces his friends in order to fulfill a mitzvah, in the end will be sent away from them honorably.
How do we know that anyone who respects his friends only for their money, in the end will be sent away from them in disgrace? For this is what we find with Bil’am the wicked, who respected Balak for his money, as it says (Numbers 22:18), “And Bil’am answered, saying to Balak’s servants: If Balak gives me his house full of silver and gold.” And how do we know he was sent away in disgrace? For it says (Numbers 24:11), “Now, get out of here and go back to your own place…for the Eternal has denied you honor.”
And how do we know that anyone who disgraces his friends in order to fulfill a mitzvah, in the end will be sent away from them honorably? For this is what we find with Moses our teacher, who disgraces Pharaoh in order to fulfill a mitzvah, as it says (Exodus 11:8), “All of your servants shall come down and bow before me, saying.” Now, was Pharaoh up on a roof and was Moses down on the ground? No, what Moses meant was: Even if all your servants who stand up (and bow) before you on your platform were to get up and beg me, I would not listen to them. And how do we know he was sent away honorably? For it says (Numbers 33:3), “On the day after the Passover offering, the Israelites went out with a raised hand.” Rabbi Matya ben Heresh went to Rabbi Yishmael ben Elazar HaKappar in Ludkia in order to learn about the four categories of atonement. He said to him: Have you heard about the four categories of atonement that Rabbi Yishmael used to teach? He replied: I have heard of three, and that repentance is essential for each one. One verse says (Jeremiah 3:22), “Return, you wayward children, says the Eternal, and I will heal your afflictions.” And another verse says (Leviticus 16:30), “On that day, he will atone for you, to purify you.” And another verse says (Psalms 89:33), “I will attend to their transgressions with my staff, and to their sins with plagues.” And another verse says (Isaiah 22:14), “This sin will not be forgiven until you die.” How do we make sense of all these? If a person transgresses a positive commandment and then repents, he is forgiven immediately. This is what is meant by “Return, you wayward children.” If a person transgresses a negative commandment and repents, the repentance is held over until Yom Kippur atones for him, as it says, “On that day, he will atone for you.” If a person transgresses a commandment for which he incurs spiritual excommunication [karet] or death by the court, and then repents, the repentance and Yom Kippur are held over until he is cleansed through suffering. This is what is meant by “I will attend to their transgressions with my staff.” But someone who profanes the heavenly Name has no possibility of repenting and waiting for forgiveness. Suffering will not cleanse him. Yom Kippur will not atone for him. They are all held over until death comes and cleanses him. This is what is meant by “This sin will not be forgiven until you die.” Isi ben Yehudah would say: Why do great Torah scholars die before their time? Not because they commit adultery, and not because they steal. Rather, it is because they disgrace themselves. Rabbi Yitzchak ben Pinchas would say: Anyone who has studied Midrash but has not studied Halakhah has never really tasted wisdom. Anyone who has studied Halakhah but has not studied Midrash has never really tasted the fear of sin.
He would also say: Anyone who has studied Midrash but has not studied Halakhah is like a strong person who is unarmed. Anyone who has studied Halakhah but has not studied Midrash is like a weak person with a weapon in his hand. Anyone who has studied both is like a person who is both strong and armed.
He would also say: Be careful when greeting other people. Do not get in the middle of a conflict, and do not try to see it. Return to a place of friends. And be a tail to lions rather than a head to foxes.