tnעוֹד (’od), an adverb meaning “yet, still,” can be inflected with suffixes and used as a predicator of existence, with the nuance “to still be, yet be” (T. O. Lambdin, Introduction to Biblical Hebrew, 171–72, §137). Then, it is joined here with the Hiphil participle מַחֲזִיק (makhaziq) to form the sentence “you are still holding them.”