Question: In regards to the month of Muharram this year, the ninth will be on a Friday and the tenth on Saturday. Is it allowed to fast Friday and Saturday?
Answer: “Yes, because he fasts a day with it. There is no harm”
Question: If I fast Thursday, three days?
Answer: “All of it is the same. Fast Thursday, Friday, Saturday. These three days is better. If he fasts one day before or after, then there is no harm”
[https://alfawzan.af.org.sa/node/15874]
Translated by
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan