Irima rirekagia riemba
The pit allows the grass to fall in
The proverb alludes to the pits the Kikuyu used to dig for trapping wild animals. These pits were covered with sticks over which, as well as over borders, they put a layer of grass. Since this grass often fell in the pit through the spaces between the sticks, so they say that often one falls into the pit dug by himself.
Hoist with his own petard.