What is the past tense of err on the side of caution?

The past tense of "err on the side of caution" is "erred on the side of caution." In this phrase, "err" is the present tense verb meaning to make a mistake or be incorrect, and "erred" is the past tense form. The expression "err on the side of caution" means to be overly cautious or careful in a decision or action.