1)
What is "Rosh Mesibai"?
1.
Rashi: A gang of Esav's troops, who say (plan) to turn me away from You.
2.
Radak: It is Do'eg, the head of the Resha'im who surround me to trap me 1 .
1
99Malbim: This is like it says "v'Sha'ul v'Anashav Oterim El David" (Shmuel I, 23:26).
2)
What is the meaning of "Amal Sefaseimo Yechasemo"?
1.
Radak: The Sheker that he and his colleagues speak about me, it will cover them and make them fall.
2.
Malbim: The injustice on their lips, the sin of Leshon ha'Ra, should descend on their heads.