GEN454 Know that the sexual intercourse of man with his wife is holy and pure when done properly, in the proper time and with the proper intention.  No one should think that sexual intercourse is ugly and loathsome, God forbid! Proper sexual intercourse is called “knowing” [this verse] for good reason.  As it is said, “And Elkanah knew his wife Hannah” Samuel 1 1:19. The secret reason for this is that when the drop of semen is drawn in holiness and purity, it comes from the source of wisdom and understanding, which is the brain.  Understand, therefore, that unless it involved matters of great holiness, sexual union would not be called “knowing.” HTBAJ 158