Pirkei Avot - Ethics of the Fathers

~Level 1~
Tiferet Yisrael - a bad neighbor - an angry person, an arrogant person , a jealous person, or the like. Not only should you not join him lest you learn from his deeds and damage your soul, but even distance from him lest he damage even your body.

~Level 1~
Rashi - "do not abandon belief in retribution" - if you are rich, do not trust in your wealth. For troubles can come quickly, as written: "Fortunate is the man who is always afraid, [but he who hardens his heart will fall into evil]" (Mishlei 28:14). So too, if troubles befall you, do not give up hope for salvation is near to come, as written: "Behold, the hand of the L-ord is not too short to save" (Isaiah 59:1).

~Level 2~
Rabeinu Yonah - "Distance yourself from a bad neighbor" - to one who looks to rent or buy a house, just like one inquires whether the house is nice and in a good location, so too, he should inquire on the neighbors. If they are bad, distance. If they are good, approach.

"do not join a wicked person" - it is a great punishment without equal. For if one committed a serious sin, it is one sin. But this person has a portion in all the sins the wicked man committed as a reward for joining his company. Thus he commits many great and severe sins even though he did nothing and did not derive any benefit. "Woe to the wicked, woe to his neighbor". Thus it is explained in Avot D'Rebbi Natan (30:3): "whoever joins the wicked receives punishment like them even though he does not do like them; whoever joins the righteous receives reward like them even if he did not do like them". On this it is written: "When you joined Ahaziah, the L-ord has broken your work" (Divrei Hayamim II 20:37).

"do not abandon belief in retribution" - do not tell yourself: "I will join the wicked now while he is in prosperity and success and when his good situation changes, I will distance from him!" You will not be able to. For you cannot know what today will bring. In an instant his calamity can come and you will be struck with him.. it is a great sin to flatter the wicked in this world... his calamity will come suddenly and you will not be able to save yourself.

~Level 2~
Rabbi Avraham Azoulai - Ahava b'Taanugim - "do not join a wicked person" - i.e. if he joins you, namely, you are primary (ikar) while he is subordinate (tafel) then it is good. For there is hope he will listen to your words since you are primary. But if he will be primary (ikar) and you will be subordinate. He will certainly not listen to your words. On this "do not join" him, i.e. when you are subordinate to him.

~Level 3~
Maharal - like Yehoshua ben Perachya, Nitai HaArbeli comes to rectify one's conduct with others outside the home. Only that Nitai HaArbeli rectifies this with mussar of Yirat Shamayim (fear of Heaven).

It is proper to ask on his words. Why bring these three things together?

The explanation is that Nitai HaArbeli came to rectify man's conduct with other people outside his home. He said to distance oneself from a bad neighbor so as not to be burned by the hot coal of a bad neighbor, as written: "woe to a wicked person, woe to his neighbor" (Negaim ch.12). Therefore "distance yourself from a bad neighbor", as written: "when you joined Ahaziah, the L-ord broke your work" (Divrei HaYamim II 20).

That which he did not use the same term throughout, such as "do not draw close to a bad neighbor, do not join with a wicked man", or "distance from a bad neighbor and from joining a wicked man". (But instead he changed terms "distance from a bad neighbor", "do not join a wicked man").

The reason is that the two are different matters. For even if he does not draw close to a bad neighbor and the bad neighbor comes to him, he needs to distance from him. This is not relevant to say by a friend "distance from a bad friend". For it is enough to not join him. For when he does not join him, he is already distant from him.

"do not abandon belief in retribution" - do not think you are distant from evil and therefore you can come close to potentially evil things and no harm will befall you. On this he said: "do not abandon belief in retribution", thus do not draw near evil.

A deeper look
"distance yourself from a bad neighbor, do not join a wicked person, and do not abandon belief in retribution" - that which he said "do not abandon belief in retribution" is also similar to "distance from a bad neighbor, etc." For evil is also like a neighbor to people. As known of the matter of evil. It dwells and is joined to existing things. Thus he said: "do not abandon belief in retribution". For evil is the neighbor of people. Therefore do not not join or go near evil for you will be harmed, and "do not abandon belief in retribution" who is close by and a neighbor of people.

This refers to inexistence (he'eder) which clings to people. It is more of a neighbor than one's (human) neighbor nearby, and nearer than your closest friend. For it sits opposite a man to destroy him. Thus, he said these three things together.

Understand their order "distance yourself from a bad neighbor, do not join a wicked person, and do not abandon belief in retribution", which is opposite man.

The latter is a warning to man to not think it is not possible for him to be struck with retribution. He did not say to worry about sufferings. For worrying about sufferings is a bad trait, as we wrote on the Netiv Habitachon with G-d's help. Rather he said "do not abandon belief in retribution", as happened to Haman.

He trusted in his great wealth and in the blink of an eye all his success flipped on him. This is the meaning of "do not abandon belief in retribution".

Some explain "do not abandon belief in retribution" as a reason for "distance yourself from a bad neighbor, do not join a wicked person". Namely, do not tell yourself: "even if I don't distance from a bad neighbor and from the wicked man, I will still be at peace. For what could possibly happen to me?"

On this he said: "do not abandon belief in retribution". For it is possible for calamity to strike suddenly. Therefore, don't say that, and because of this "Distance yourself from a bad neighbor, do not join a wicked person".

All this is coming to exhort on fear of Heaven (yirat shamayim) so that he does not come to sin. For without a doubt, a bad neighbor and a wicked friend bring a person to sin.

Thus, Yehoshua ben Perachya (previous mishna) came to rectify man's conduct with those who are outside his home but relevant to him, such as the Rabbi, friend, and other people. This was a rectification and branch from the side of love of G-d.

Here Nitai HaArbeli came to rectify man in fear of G-d in things opposite to this, namely, the wicked. Thus, "distance yourself from a bad neighbor, etc."

Hence, both of their teaching is on one matter...