Unyawu aluna mpumulo - Literally: The foot does not have a nose.

Background.

This is said of a smart-aleck type of a guy, who eventually walks into a trap as a well deserved “serve him right” situation.

… because had he known, where his feet were taking him, they would have smelled the trouble and gave him due warning to keep off; as it were feet do not have olfactory faculties and through his own advice he walked into a sticky situation.

So it sometimes reads: The wise guy eventually walks into trouble of his own making.