Rashi (2): They do not speak with people. Rather, in the entire land their rays go out and illuminate for creations. Amidst this, people tell the honor of Hashem and thank and bless for the luminaries.

Radak #1 (2): They do not speak via words. Rather, from what man sees in them, people tell the honor of Hashem.

Radak #2 (2): They are not words like people's words. Rather, the actions that they do are the Devarim and telling.

Radak (2, citing Moreh ha'Nevuchim): The telling is not via mouth and words, rather, like a picture in the heart or praise and thanks, without language.

Malbim: (These are connected to the end of the verse.) These matters are not silent, for there is no Omer (complete saying) or Devarim (even isolated words) "Bli Nishma Kolam." Rather, every exception to nature and all new wonders every moment to testify about the Creator's honor, their voice is heard from one end of the land to the other. Every bush, vermin and motion in the world has a great voice and announces the Creator's greatness and Chachmah.