Rashi interprets Mizmor 12 which discusses the danger of words as a historical reference to David’s life. Radak, noting the lack of a personal plea, believes that this is a general description or prophecy for the future. Malbim changes the focus from using one’s language to cheat to using one’s language to reject God.

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion