Ta'anit Bechorim - Fast of the Firstborn This symbolic fast of thanksgiving commemorates the deliverance of the Israelites' firstborn during the 10th plague in Egypt prior to the Exodus. The obligation to fast is so limited that the rabbis introduced the participation of first born males in a religious ceremony to mark the end of study of a tractate of Talmud in order alleviates the necessity of their fasting in practice.