Do you believe that Messianic Believers should keep the New Moon?
The New Moon or Rosh Chodesh is not listed as one of the Lord’s appointed times of Leviticus 23. However, because the Hebrew rosh chodesh means the same as “new month,” determining the rosh chodesh is important as it relates to the timing of the Biblical festivals. Prophetically, in the Millennial Reign of Yeshua, Rosh Chodesh is to be a time of great rejoicing and festivity: “‘And it shall be from new moon to new moon and from sabbath to sabbath, all mankind will come to bow down before Me,’ says the LORD” (Isaiah 66:23).
The problem with “keeping” the New Moon is that the Bible itself is by-and-large mute on how we are to keep it. Numbers 29:6 describes “the burnt offering of the new moon and its grain offering.” Psalm 81:3 says, “Blow the trumpet at the new moon, at the full moon, on our feast day.” And the New Moon is mentioned in Colossians 2:16, “Therefore no one is to act as your judge in regard to food or drink or in respect to a festival or a new moon or a Sabbath day.” Because of the lack of information in the written Scriptures themselves about what do about the New Moon, we are forced to turn to Jewish custom and tradition. The JPS Guide to Jewish Traditions states the following concerning Rosh Chodesh:
“Rosh Hodesh (lit., ‘head of the month’) is the first day of the month, which correlates with the sighting crescent of the new moon. In a lunar calendar, each month has a little more than 29 days…Originally it was the Sanhedrin’s task to determine whether a particular month had 29 or 30 days, based on the visual observation of witnesses. The members of the Sanhedrin gathered on the 30th of each month and awaited testimony. If witnesses appeared, Rosh Hodesh was celebrated, and that day was counted as the first day of the next month. If no witnesses appeared, the next day was celebrated as Rosh Hodesh. To spread word that the new month had begun, fires were lit on the Mount of Olives and then successively throughout Israel. Jews living far from Jerusalem always celebrated Rosh Hodesh on the 30th day of the month. When informed that it had been postponed to the next day, they also celebrated that day.
“In ancient times, Rosh Hodesh was considered an important holiday, observed with great seriousness. Work was suspended, special sacrifices were offered in the Temple, the shofar was blown, and it was customary to visit the prophet….
“After the destruction of the Temple, the power to declare the day of the New Moon passed to the head of the court at Yavneh. During the fourth century C.E., however, the Christian authorities in the Land of Israel prohibited the dissemination of information regarding the day of the New Moon. Consequently, in about 360, Hillel II published a fixed calendar based on astronomical calculations…thus freeing Jewish communities from having to rely on the declaration by the high court in the Land of Israel.
“….Although the importance of Rosh Hodesh as a religious festival has declined and it retains only a shadow of its former prominence, the Rosh Hodesh service contains three liturgic elements that raise it to the level of the intermediate days of the major festivals. Ya’aleh v’Yavo…is included in the morning Amidah…, the half Hallel is recited…, and there is a Musaf service that recounts the sacrifices that were offered in the Temple on that day. As a joyous, though minor, festival, Tachanun…is not recited, fasting is forbidden, any funeral service is abbreviated, and it is tradition to partake in a festive meal.”
Many of those in the independent Messianic community who attempt to observe Rosh Chodesh do not tend to observe it as described above. While the New Moon is to be observed to determine when a New Month begins, in Biblical times it was to be validated by the Sanhedrin. Today, the closest thing we have to the Sanhedrin are the Rabbinical Jewish authorities who publish the Jewish calendars that are used today. If we are to observe Rosh Chodesh, it must be with this in mind, as Yeshua did validate us taking the lead of the Pharisees, recognizing that they sat in Moses’ seat (Matthew 23:1-3). The Pharisees today would be represented in the Jewish authorities, and any future Sanhedrin that may be established to determine when the New Moon is and when the dates are for us to celebrate the appointed times or moedim. We should observe Rosh Chodesh the same way as the Jewish community.
 Ronald L. Eisenberg, The JPS Guide to Jewish Traditions (Philadelphia: Jewish Publication Society, 2004), 166-167.