מדרש על ישעיהו 55:12

But in the end, the peoples will praise Israel (for the fulfillment of their faith in the L-rd), viz.: "The nations will praise His people." And whence (do we derive the same for) heaven and earth? From (Isaiah 44:23) "Sing, O heavens, for the L-rd has wrought; shout (for joy), foundations of the earth!" And whence, mountains and hills? From (Ibid. 55:12) "The mountains and hills will break out in song before You, and all the trees of the field will clap hands." And whence, the (fore-) fathers and mothers? From (Ibid. 42:11) "The dwellers of the rock will sing; from the peaks of the mountains will they shout."