1,254. Declaring a Month Full Out of Necessity

Hilchos Kiddush HaChodesh 3:17

If the court needed to leave the month full as it was before the witnesses arrived, then it is left alone. This is what is meant when tractate Rosh Hashana refers to the month being declared full out of necessity. Some authorities disagree about this and are of the opinion that the month is never made full out of necessity. Rather, if witnesses arrive, the month is sanctified without subjecting them to an intimidating interrogation.

Hilchos Kiddush HaChodesh 3:18

The Rambam says that the authorities only seem to disagree in this matter when it comes to months other than Nisan and Tishrei, or when witnesses arrive in Nisan or Tishrei after the holidays, with their various practices and offerings, are already over. If witnesses arrive in Tishrei or Nisan before the middle of the month, their testimony is accepted without subjecting them to an intimidating interrogation at all. This is because we don’t try to intimidate witnesses who testify that they saw the moon in its proper time in order to declare the month full.