The Holy Trinity of Jewish Superstitions

The Gemara cites three things which Rava instructed his sons. Rava said to his sons when you cut meat do not cut it upon your hand, do not sit on the bed of an Aramean woman, and do not pass behind a synagogue when the congregation is praying.

The Gemara gives two reasons for not cutting meat on your hand. There are those who say that one should not do so because of the danger that one may sever his hand and there are those who say that even if we are not afraid that he will maim himself, even a small cut will cause him to bleed into the food, causing those sitting around the table to be repulsed. Thus he should not slice meat on his hand because his carelessness may be the ruin of the meal.

The Gemara then explains why not to sit on the bed of an Aramean woman with three explanations. There are those who say he meant do not go to sleep without first reciting Shema. Rashi says that without the Shema's recital your bed is similar to that of an Aramean. There are those who say this means that one should not marry a female proselyte. This brought us to our first question. We thought that it was okay to marry a convert, but here Rava says not to? The answer is found in the Even Haezer. According to the Iyun Yaakov, Rava and his sons were Kohanim and they were therefore forbidden to marry converts. Rava's point in his instruction was to stress this prohibition to his sons

There are those who say this literally means that one should not sit on the bed of an Aramean woman, because of the following incident involving Rav Pappa. Rav Pappa once went to the home of an Aramean woman to collect an outstanding loan. She brought out a bed for him and said for him to sit. Rav Pappa said I will not sit until you lift up the bed so I can see what is underneath. She lifted the bed up and they found a dead child. This brings us to our second question. Where in the world did a dead child come from, why would the Aramean put a dead child there in the first place, and how the hell did Rav Pappa know to look for a dead child? The answer to all three of these is found in Rashi. Rashi cites an incident where Rav Pappa lent a sum of money to an Aramean man (some say that it does not just mean a woman). Rav Pappa demanded the repayment. The Aramean resented his claim so he plotted to falsely implicate Rav Pappa in some crime and thereby indirectly rid himself of his debt. He took the corpse of a small child and laid it on his bed covering it with clothes so that no one would realize what lay underneath. He then invited Rav Pappa to his home telling him that he would give him the money. Rav Pappa went with him and in the house the Aramean said to sit but Rav Pappa recognized his deceit and found the dead child.Based on this the sages said that it is forbidden to sit on the bed of an Aramean woman.

The Gemara now discusses the reason of not walking behind a synagogue in the middle of prayers.The statement by Rava lends support to R'