Rosh Chodesh Kislev

Rosh Chodesh or Rosh Hodesh (Hebrew: ראש חודש; trans. Beginning of the Month; lit. Head of the Month) is the name for the first day of every month in the Hebrew calendar, marked by the birth of a new moon. It is considered a minor holiday, akin to the intermediate days of Passover and Sukkot.

Origin

The Book of Exodus establishes the beginning of the Hebrew calendar:
"And the LORD spoke unto Moses and Aaron in the land of Egypt, saying: 'This month shall mark for you the beginning of the months; it shall be the first of the months of the year for you.'" (12:1-2)

In the Book of Numbers, God speaks of the celebration of the new moon to Moses:
"And on your joyous occasions - your fixed festivals and new moon days - you shall sound the trumpets over your burnt offerings and your sacrifices of well-being." (10:10)

In Psalm 81:3, both new and full moon are mentioned as a time of recognition by the Hebrews:
"Blow the trumpet at the time of the New Moon, at the full moon, on our solemn feast day. For this is a statute for Israel, a law of the God of Jacob."

The occurrence of Rosh Chodesh was originally confirmed on the testimony of witnesses observing the new moon. After the Sanhedrin declared Rosh Chodesh for either a full month or a defective, 29-day month, news of it would then be communicated throughout Israel and the diaspora.

A custom was developed in which an additional day could be added to the month to ensure that certain holidays (such as Yom Kippur) did not fall on the days before or after Shabbat.

The Month of Kislev

Beginning of new Hebrew month of Kislev. The name "Kislev" is of Babylonian origin. Kislev is the 9th month of the Hebrew year. Corresponds to November or December on the Gregorian calendar.

In the Tanach (Bible), Kislev is referred to as the ninth month, as it is the ninth month after Nisan. Although most famous for having Chanukah within it, Kislev is also a month with significant Biblical happenings.

The first rainbow, observed after the Flood, was seen in Kislev. "And G-d said: ‘This is the sign of the covenant which I set between Me, and yourselves, and between every living being that is with you, unto eternal generations. I have placed my bow in the cloud, and it shall be a sign of a covenant between Me and the Earth’". "This is the sign of the covenant" – G-d showed Noah the bow and said to Him: "This is the sign of which I spoke" (Bereishit 9).

Rosh Chodesh Kislev, which refers to the transition day or days between months, consists at times of one day, and at times of two. The preceding month of Cheshvan sometimes consists of twenty nine days, and sometimes of thirty days. In the former instance Rosh Chodesh Kislev consists of one day, which is the first of Kislev; in the latter, of two, with the first day of Rosh Chodesh counting also as the 30th day of Cheshvan, and the second day of Rosh Chodesh counting as the first day of Kislev.

From the days of the Hasmoneans, as long as the Beit Din, also known as the Sanhedrin, or Jewish Supreme Court, sanctified the month through the testimony of witnesses, who testified as to when they had seen the New Moon, where in the sky they had seen the New Moon, and exactly what it looked like, messengers of the Beit Din went out to places distant from Yerushalayim, to make known when the new month had been sanctified.

The Beit Din needed to do this only during months in which festivals occurred, so that people knew on which day to observe the festival. Therefore, when the month of Kislev was sanctified, messengers were sent out, so that people living far from Yerushalayim would know when Chanukah was to begin. Chanukah has the status of a festival, although it is Rabbinic in origin, and not directly mentioned in the Torah.