[93b bottom] Rabbah bar Chiya of Ketusphaa quoting Rabbah: One who picks pebbles out of the wheat in his fellows granary must pay him the value of his wheat equivalent to the volume of pebbles removed.
see Prac-T-cal Tidbits: We are held accountable for each and every little ‘pebble’ that we pick. Nothing is ever too insignificant to be noteworthy (even if it may not be punishable in a physical court of law). We should look out for other’s property as we would want our own protected, and apply this standard to Mitzvos as well. Treat dust like diamonds, and greatness will glow.