What is the significance of the allusion, "The thing that Saul's daughter had done to David"?
As my colleague mentioned above, the allusion is a biblical one. In 2 Samuel, Chapter 6, King David is so happy about bringing the ark of God to the city of David that he can't help dancing for joy. Michal, his wife, sees him dancing and thinks that he is making a fool of himself. In her opinion, he is the king of Israel and should exhibit a certain dignity pertinent to his exalted position.
When she finally sees David, Michal sneeringly comments that he must be proud to dance like a commoner before all the servants, especially the female ones. King David doesn't take too kindly to her comments; he basically retorts that he will continue dancing in any way he likes. After all, he asserts that God chose him to be king, so he doesn't care what she thinks of his wild dancing. Sound familiar? The exchange demonstrates the bitter and contentious relationship between King David and Michal.
It also perfectly explains the fractious relationship between Janie and Jody. Allusions are references to cultural, political, or historical subject matters of significance. They are often used as literary devices to briefly and effectively explain complex emotions or ideas. The biblical reference above explains how deep the fissures are in Janie and Jody's relationship.
In Chapter Seven, Jody has been making Janie's life miserable. Jody knows that he is deteriorating physically and mentally, so he tries to make himself feel better by attacking Janie and being emotionally abusive to her. Janie eventually tires of Jody's antics and fights back. They trade barbs about each other's looks. Eventually, Janie voices the same kind of contempt for her husband that Michal voiced for King David. However, the narrator tells us that she did far worse.
But Ah’m uh woman every inch of me, and Ah know it. Dat’s uh whole lot more’n you kin say. You big-bellies round here and put out a lot of brag, but ’tain’t nothin’ to it but yo’ big voice. Humph! Talkin’ ’bout me lookin’ old! When you pull down yo’ britches, you look lak de change uh life.
Janie had robbed him of his illusion of irresistible maleness that all men cherish, which was terrible. The thing that Saul’s daughter had done to David. But Janie had done worse, she had cast down his empty armor before men and they had laughed, would keep on laughing.
So, the biblical allusion not only explains the complex dynamics between Janie and Jody, it also provides a reference to compare the depth of Janie's insult. Jody's physical retaliation is swift and terrible, precipitating the irretrievable breakdown of their marriage.
Saul's daughter Michal first married David but then had a falling out with him over family matters, left him and married another man. David went after her, though, and forced her to come back in spite of the protestation and weeping of her present husband.
Micah seemed to never be fully reconciled to David as later it is recounted that she "despised him in her heart" when he was worshipping God, even dancing in joy. But let it also be said that David had also other wives with whom he could find consolation!
To see the specific Biblical passages related to David and Michal's turbulent relationship, visit the last site posted below.