What is the meaning of "Heref me'Af"?
Rashi: Refrain from doing evil, lest [Divine] anger come upon you.
Radak: Do not be angry at Hashem if He does not direct your ways like your desire. A fool does so - "Iveles Adam Tesalef Darko v'Al Hashem Yiz'af Libo" (Mishlei 19:3).
Radak citing R. Shlomo ben Gevirol: Abandon the Midah of anger.
Malbim: Even if success is far from you, do not be angry at Hashem.
What is the meaning of "va'Azov Chemah"?
Rashi: Refrain from doing something that will bring Hashem's wrath on you.
Radak: The matter is repeated in different words.
Radak citing R. Shlomo ben Gevirol: Regret what this Midah (anger) took effect on you.
Malbim: Abandon also Chemah, which is inner anger in the heart.
Why does it say "Al Tischar Ach Lehare'a"?
Radak: Do not mingle with Resha'im to do evil deeds, because you see their success. "Ach" - do what you will, just do not be involved with an evil deed. The same applies to "Ach ba'Shem Al Timrodu" (Bamidbar 14:9).
Malbim: Do not compete in any way; this will only do evil to you. It is better to be an Oni who trusts [in Hashem] than an Ashir who does not trust, for "the end of a matter is better than its beginning" (Koheles 7:8) - then 1 will be seen the difference between evildoers and those who trust in Hashem.
It seems that 'then' is at the end of days. (PF)