I have made the intention to fast the first ten days of Thul-Hijjah. I work ten hours a day, and I may not be able to keep up with what I have intended. Can I fast the day of ‘Arafah only?

All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Fasting the first ten days of Dhul-Hijjah is not obligatory; rather, it is recommended. Hafsah said:

There are four things that the Prophet, sallallaahu ‘alayhi wa sallam, never missed: fasting ‘Ashoora’ (the tenth day of Muharram), fasting the first ten days of Thul-Hijjah, fasting three days every month, and a two-rak‘ah-prayer before noon. [Ahmad, An-Nasa’i and Ibn Hibban; Ibn Hibban: Sahih (authentic)]

Muslim scholars deduce from this hadith that fasting the first ten days of Thul-Hijjah is recommended. The mere intention of fasting these days does not make it obligatory, as long as one does not make a vow to fast them. That being said, there is no problem if you fast the day of ‘Arafah only. 

Allah knows best.