There are companions to keep one company,
And there is a friend more devoted than a brother.

Joshua ben Perahiah and Nittai the Arbelite received [the oral tradition] from them. Joshua ben Perahiah used to say: appoint for thyself a teacher, and acquire for thyself a companion and judge all men with the scale weighted in his favor.

(11) Now when Job’s three friends heard of all this evil that was come upon him, they came every one from his own place, Eliphaz the Temanite, and Bildad the Shuhite, and Zophar the Naamathite; and they made an appointment together to come to bemoan him and to comfort him.

One who learns from his fellow one chapter, or one halakhah, or one verse, or one word, or even one letter, is obligated to treat him with honor; for so we find with David, king of Israel, who learned from Ahitophel no more than two things, yet called him his master, his guide and his beloved friend, as it is said, “But it was you, a man mine equal, my guide and my beloved friend” (Psalms 55:14). Is this not [an instance of the argument] “from the less to the greater” (kal vehomer)? If David, king of Israel who learned from Ahitophel no more than two things, nevertheless called him his master, his guide and his beloved friend; then in the case of one who learns from his fellow one chapter, or one halakhah, or one verse, or one word, or even one letter, all the more so he is under obligation to treat him with honor. And “honor’” means nothing but Torah, as it is said, “It is honor that sages inherit” (Proverbs 3:35). “And the perfect shall inherit good” (Proverbs 28:10), and “good” means nothing but Torah, as it is said, “For I give you good instruction; do not forsake my Torah” (Proverbs 4:2).

And acquire for yourself a friend. How so? This teaches that a person should acquire a friend for himself who will eat with him, and drink with him, and study Scripture and Mishnah with him, and go to sleep with him, and tell him all his secrets, both secrets of the Torah and secrets of the ways of the world. For when they sit and engage in Torah together, and one of them makes a mistake in the law, or the division of chapters, or declares an impure thing pure, or a pure thing impure, [or a forbidden thing permitted or a permitted thing forbidden, then his friend will correct him. And how do we know] that when his friend corrects him and studies with him, that they will have great reward from their studies? For it says (Ecclesiastes 4:9), “The two are better than the one, for they have great reward from their efforts.”

As iron sharpens iron
So a man sharpens the wit of his friend.

The Gemara cites other expositions that deal with Torah study. Rabbi Ḥama, son of Rabbi Ḥanina, said: What is the meaning of that which is written: “Iron sharpens iron, so a man sharpens the countenance of his friend” (Proverbs 27:17)? This verse comes to tell you that just as with these iron implements, one sharpens the other when they are rubbed against each other, so too, when Torah scholars study together, they sharpen one another in halakha.

Rabbi Chama Bar Chanina opened with the following verse: Iron sharpens iron (Proverbs 27:17). Rabbi Chama Bar Chanina said: A knife will only become sharpened only at the side of another. So too, a Torah scholar can only become sharpened by a friend. "Iron sharpens iron and a person sharpens the face of his neighbor." This is referring to Jacob. When our father Jacob stood together (play on sharpened) with his friend, the Shekinah attached itself (or sharpened) to him. As it says "Behold Adonai stood upon him" (Genesis 28:13).

As [with] water: the face [that you "show" it] is the face [it shows you]; so the heart of a man [i.e., the love he shows his friend] is the [(heart of the)] man [that he gets in return].

The Gemara asks: And what is all this? Why did they go to such extreme lengths to avoid being discovered? The Gemara answers: It is as Mar Zutra bar Toviya said that Rav said, and some say that Rav Huna bar Bizna said that Rabbi Shimon Ḥasida said, and some say that Rabbi Yoḥanan said in the name of Rabbi Shimon ben Yoḥai: It is preferable for a person to deliver himself into a fiery furnace so that he not whiten the face of, i.e., embarrass, his friend in public. From where do we derive this? From the conduct of Tamar, as it is written: “And Judah said: Bring her forth, and let her be burnt. When she was brought forth, she sent to her father-in-law, saying: By the man, whose these are, am I with child” (Genesis 38:24–25). Although Tamar was taken to be executed by burning, she privately and directly appealed to Judah, rather than publicly identifying him as the father of her unborn children and causing him embarrassment.

"Make for yourself a mentor": He means to say even if he is not fit to be your mentor; still place him upon you as a mentor, so that you can give and take (discuss and argue) with him, and as a result of this the study of wisdom will come to your hand. As the study of a man on his own is good, but his study from someone else will be better established in his hand and it will be more clear - and even if he is like him in wisdom or below him. And so did they elucidate the explanation of this commandment. And he said, "acquire for yourself a friend". He said it with an expression of acquisition and he did not say, "Make for yourself a friend," or "Befriend others." The intention of this is that a person must acquire a friend for himself, so that all of his deeds and all of his matters be refined through him, as they said (Taanit 23a), "Either a friend or death." And if he does not find him, he must make efforts for it with all his heart, and even if he must lead him to his friendship, until he becomes a friend. And [then] he must never let off from following [his friend's] will, until his friendship is firmed up. [It is] as the masters of ethics say, "When you love, do not love according to your traits; but rather love according to the trait of your friend." And when each of the friends has the intention to fulfill the will of his friend, the intention of both of them will be one without a doubt. And how good is the statement of Aristotle, "The friend is one." And there are three types of friends: a friend for benefit, a friend for enjoyment and a friend for virtue. Indeed, a friend for benefit is like the friendship of two [business] partners and the friendship of a king and his retinue; whereas the friendship for enjoyment is of two types - the friend for pleasure and the friend for confidence. Indeed, the friend for pleasure is like the friendship of males and females and similar to it; whereas the friend for confidence is when a man has a friend to whom he can confide his soul. He will not keep [anything] from him - not in action and not in speech. And he will make him know all of his affairs - the good ones and the disgraceful - without fearing from him that any loss will come to him with all of this, not from him and not from another. As when a person has such a level of confidence in a man, he finds great enjoyment in his words and in his great friendship. And a friend for virtue is when the desire of both of them and their intention is for one thing, and that is the good. And each one wants to be helped by his friend in reaching this good for both of them together. And this is the friend which he commanded to acquire; and it is like the love of the master for the student and of the student for the master.

One who sees his friend after thirty days, says shehecheyanu (who has kept us alive....) and after twelve months, one blesses m'chayeh meytim (who gives life to the dead) and this is for one who is very dear to him and is happy when seeing him.