Answer:
All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Fulfilling a vow is one of the acts which draws a person closer to Allah, yet it is not obligatory, but if you bound your intention with it, then you are obliged to fulfill since Allah, The Exalted said (What means):”Let them perform their vows.” [Al-Hajj/29]. In addition, the Prophet (PBUH) said (What ):” Whoever vows to obey Allah, let him obey Him. Whoever vows to disobey Allah, let him not disobey Him." [Related by Al-Bukhary].Therefore, whoever took a vow to fast for one consecutive month is obliged to fulfill it literally and if he missed a day within this month is obliged to fast the whole month consecutively once again.
