In today’s Rambam, we are finishing the halachos of Kiddush Hachodesh! In perek Yud-Ches and Yud-Tes, we learn more about how the Beis Din knows if the witnesses are telling the truth that they saw the moon. They make calculations to figure out if it is possible to see the moon on a certain night.

But just because there IS a new moon doesn’t mean that anyone can see it! Sometimes the moon is very low in the sky and someone needs to be on top of a mountain to see it, or it might be hidden behind clouds.

The Rambam explains what the Beis Din does if nobody sees the moon for many months — they can’t just make every month be 30 days long, because that will mess up the calendar! The Beis Din follows a pattern, like we do nowadays: one long month, and then one short month. That way, even if there are no witnesses, the Yidden will all be keeping a proper calendar.

One of the questions the Beis Din asks people is, “Which way was the moon pointing when you saw it?” The Rambam explains how the Beis Din knows if their answer makes sense: It depends on where the sun is! The part that we can see of the moon is because the sun is shining on it and making it lit up. (You can try this yourself using a ball and a flashlight in a dark room!)

The sun’s “path” (orbit) around the earth and the moon’s orbit aren’t like two circles on a flat piece of paper. They are both tilted in different directions, so sometimes the sun is a little bit higher or lower in the sky than the moon is. Since it is shining down at the moon, or up at the moon, it makes the moon look like it’s pointing in a different direction! (You can try this with your flashlight too!)

The Rambam tells us how to calculate this ourselves, so we can know which way the moon should be pointing on Rosh Chodesh.

We also learn the first perek of a new set of halachos about fasts that the Chachomim make for the whole town. If something scary happens, we need to daven to Hashem of course, and also fast to ask for Hashem to help us. The Rambam talks about WHO needs to fast, and WHEN we’re not supposed to make this kind of fast.

The Rambam says that if a person says that something just happened by chance, it is cruel! Hashem wants us to do teshuvah, and by saying that it was just by nature, it will stop us from doing teshuvah properly, and we won’t be able to get all of Hashem’s special brachos.

We aren’t allowed to buy something that probably was stolen. For example, we aren’t allowed to buy something from a person who tells us to hide it, or from a person who usually doesn’t have that kind of thing, unless we are SURE it belongs to them!