Who originally sings "if you don't know me by now"? it is under percy sledge, the ojays, michael bolten, marvin gaye, harold actually sang this? i know michael bolten did a remake, but i am looking for the original.

Acurious child asked his mother: “mommy, why are some of your hairs turning grey? ” the mother tried to use this occasion to teach her child: “it is because of you, dear. every bad action of yours will turn one of my hairs grey! ” the child replied innocently: “now i know why grandmother has only grey hairs on her head.”