Luke 11:35

Take heed therefore that the light... — Better, See to it whether the light that is in thee be darkness. This takes the place in St. Luke’s report of St. Matthew’s (Luke 6:23) “If the light that is in thee be darkness, how great is that darkness!” The warning is one which calls men to self-scrutiny. They need to examine their primary beliefs, their very intuitions of right and wrong, lest all they do should be vitiated at its very source. The call to do this implies that they must have a Light by which to judge their light, a Standard by which to test their standard, and that Light and Standard are found in the teaching of the Light that lighteth every man, in the recorded words and acts of the Son of Man.