The use of phrases like as so-and-so said or as the saying goes suggests that the quote that follows has just been illustrated
Such phrases are inappropriately used when an apparent counterexample has just been given
Harold's friends were surprised when he revealed that he had left his wallet at home and asked that someone lend him money. But he had done the same thing many times before. As Halliard said, The force of selfishness is as inevitable and as calculable as the force of gravitation. 