Avos 2:9 צְאוּ וּרְאוּ אֵיזוֹהִי דֶרֶךְ יְשָׁרָה

He [Rabban Yohanan] said unto them: go forth and observe which is the right way to which a man should cleave? Rabbi Eliezer said, a good eye; Rabbi Joshua said, a good companion; Rabbi Yose said, a good neighbor; Rabbi Shimon said, foresight. Rabbi Elazar said, a good heart. He [Rabban Yohanan] said to them: I prefer the words of Elazar ben Arach, for in his words your words are included. He [Rabban Yohanan] said unto them: go forth and observe which is the evil way which a man should shun? Rabbi Eliezer said, an evil eye; Rabbi Joshua said, an evil companion; Rabbi Yose said, an evil neighbor; Rabbi Shimon said, one who borrows and does not repay for he that borrows from man is as one who borrows from God, blessed be He, as it is said, “the wicked borrow and do not repay, but the righteous deal graciously and give” (Psalms 37:21). Rabbi Elazar said, an evil heart. He [Rabban Yohanan] said to them: I prefer the words of Elazar ben Arach, for in his words your words are included.

"A good eye": One who suffices with what he has and does not seek extraneous things - and is not envious when he sees that his fellow has more than him.

"should cling, etc.": Its explanation is that certainly one should cling to all of the good and straight [character traits], but rather he meant to say in one trait should [a person be] always complete. As it is better for a person to grab on to one trait completely always - and it makes it easier for him to achieve all of the important good traits - than for him to have a few character traits and not to be complete in any of them - the teacher, Rabbenu Yonah. And the lips should kiss [this] - Midrash Shmuel. And it works well with this that the words of Rabbi in the beginning of this chapter refer to all of the traits, [and discusses] what is the path that a person should choose, such that he can enact [it] in the doing of each and every [character trait]. That is why he did not say, "cling."

Rabbi Yehoshua says: A good friend: That he cling to this straight path and it become easy for him to do it; and to be a good friend to the man that his heart desires, and to accustom himself that a (another) spirit be pleased from him. And thus he will come to be [on friendly terms] with all of the creatures.

Rabbi Yosi says: A good neighbor: That he himself be a good neighbor to all of his neighbors. And once he becomes good and a loyal friend to five or eight people, the matter is close for him to love all that come to the world. And [so] he is happy and with all of the good traits.

"Seeing the consequences of one's actions": One who looks out and sees what will be in the future. And through this, he calculates the loss [engendered by doing] a commandment versus its reward and the reward [engendered by doing] a sin versus its loss.

And one must say that that which [Rabbi Bartenura] said above, "and from this, he calculated, etc." is not the main understanding of "seeing the consequences;" but rather, that from it also extends that "he calculates, etc." But the main intention of "seeing the consequences" is that which he explains [first], "One who looks out and sees what will be in the future" - and this is in all of his matters and dealings, etc. And see Tosafot Yom Tov.

Rabbi Shimon says: Seeing the consequences of one's actions: That he places his eyes on everything, and see all of the things that will be generated before they are generated. And when he sees something that has reward at its beginning but its end will bring a loss, he will distance himself from it. And with this, he will never sin - as he will 'weigh the gain [that may be obtained through the committing] of a transgression against the loss [that may be sustained] by [committing] it.' And hence a person should cling to this path to weigh at the beginning that which will be at the end, and to weigh all of his affairs with this [approach].