The words "will never perish" can be supplied to each of these phrases. This can also be expressed in positive terms. Alternate translation: "the law will never perish from the priests, and advice will never perish from the wise men, and words will never perish from the prophets" or "the priests will always have the law, the wise men will always give advice, and the prophets will always speak" (See: [[rc://en/ta/man/translate/figs-ellipsis]])
Here "words" represents messages that the prophets speak from Yahweh. Alternate translation: "words of Yahweh from the prophets" (See: [[rc://en/ta/man/translate/figs-explicit]])
The people speak of speaking harmful words against Jeremiah as if their words were weapons with which they attack him. Alternate translation: "say things that will harm him" (See: [[rc://en/ta/man/translate/figs-metaphor]])