It is highly unlikely that Moses, Hillel even Maimonides (all experts on Jewish law) ever worried about what to write on a child’s birthday cake.

But different societies have different norms, and, today, a birthday cake with a delightfully sugary “Happy Birthday” is standard for any birthday celebration. For Jews observing the laws of keeping the Sabbath, however, the words on the cake may* present an interesting challenge. To break the words while cutting the cake may fall into the category of mo’chaik, erasing – one of the 39 m’la’chot (creative acts forbidden on Shabbat).

The forbidden act of mo’chaik is mentioned in a listing of m’la’chot in Talmud Shabbat 73a and is elaborated on page 75b: “Our Rabbis taught: If one writes one large letter in the place where there is room for two, he is not culpable. If he erases one large letter and there is room in its place for writing two, he is culpable. Said Rabbi Menahem son of Rabbi Jose: And this is the greater stringency of erasing over writing.”

Erasing is considered a constructive act because the builders of the Tabernacle would erase incorrect letters marked on the boards (for ease of assembly) and mark them correctly. The m’la’cha itself prohibits the obliteration of letters or characters and cleansing a writing surface.

Avoiding mo’chaik on Shabbat merely requires that one pay attention and be careful with details. For instance, when opening a package of food, one should try to avoid tearing any letters or breaking any words. (The tear may, however, go between two words). As for birthday cake, either cut between the words (but the piece may be huge…) or write the birthday message on a removable cookie!

*There are many differing opinions on this subject and one should consult one’s own rabbi with specific questions.

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