Assalam Alaikum. My question is about fasting and intention. I was making up some of the fasts that I had missed in ramadan because of a valid reason. I had decided one day that I would fast the next day and that would be one of my make up fasts. But then I realised later on that I could not fast the next day because I had an event and so I changed my intention and decided to make the fast up on another day. Does it matter that I made the intention to fast a missed fast on a certain day and then decided to not fast on that day but on another day instead. Once I made the intention to do a make up fast on a certain day is it a sin to change my intention and to fast it on another day.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger.

As long as you did not start fasting, there is no harm in not fasting even if you made intention to fast. This is similar to if you made Wudhoo’ to pray at the earliest time of prayer but had not yet started praying by pronouncing the Takbeerat Al-Ihraam. It would not then be obligatory for you to pray at that time, and you could pray after the earliest time of prayer.

However, it is forbidden to break an obligatory fast after starting it. The Kuwaiti Encyclopedia of Fiqh reads,

“It is incumbent on a Muslim of full legal capacity to complete the obligatory fast if he has started it and it is impermissible for him to break or invalidate it before the end of the fast day.”

The important thing is that you make up for the missed fast days of the previous Ramadan before the following Ramadan comes in, because the majority of the jurists held that it is impermissible to delay making up for missed fast days from Ramadan until the following one comes in with no valid excuse. It has been narrated that ʻAa’ishah said, “I owed fasts from the month of Ramadan, and I did not make up for them until Shaʻbaan came because I was too busy with the Messenger of Allaah, sallallaahu ʻalayhi wa sallam, to fast.” [Al-Bukhari and Muslim]

Al-Haafith Ibn Hajar wrote, “It is derived from her keenness to make up for the missed fast days of Ramadan in Shaʻbaan that it is impermissible to delay making up for missed fast days from Ramadan until the following one begins.” [Fat-h Al-Baari]

Allaah Knows best.