Albert Barnes Commentary Proverbs 26:7

"The legs of the lame hang loose: So is a parable in the mouth of fools." — Proverbs 26:7 (ASV)

Or, take away the legs of the lame man, and the parable that is in the mouth of fools: both are alike useless to their possessors. Other meanings are:

1. “The legs of the lame man are feeble, so is parable in the mouth of fools.”
2. “the lifting up of the legs of a lame man, that is, his attempts at dancing, are as the parable in the mouth of fools.”