One might think that one must tell the story of the Exodus on Rosh Hodesh: One might conclude that this is the case because according to Rabbi Shimon ben Gamliel, one must begin to expound on the laws of Passover two weeks before the holiday. Similarly, the Torahsays, ‘This month shall be the beginning of months for you,’ suggesting that one should begin telling the story of the Exodus from Rosh Hodesh.