What are "Ash and Sas"?
Rashi: They are kinds of worms.
Radak: Sas is the brother of (a very similar species to) Ash.
Who will be consumed?
Radak: The Resha'im. They evil that comes upon them will consume them, like moths consume a garment. This supports the Rambam's Perush (refer to 51:6:2:6).
Malbim: Those who revile you will be a garment that moths consume.
Why does it say "vecha'Tzener Yochlem Sas"?
Malbim: Those who revile your Torah will be like wool that moths consume before it is a garment. They totally dissolve it. Their punishment will be greater [than that of those who revile you].
Why does it say "v'Tzidkasi l'Olam Tihyeh [vi'Yshu'asi l'Dor Dorim]"?
Radak: The Resha'im will perish, and you will be in it forever, due to My Tzedakah and salvation that I will give to you.
Malbim: My Tzedakah will be forever, and My salvation will come in one of the generations, and last for all generations.
