It is recommended to fast on the 9th of Muharram along with the 10th of Muharram. Because, this is the teaching of the Prophet (ﷺ).
A hadith from Al-Hakam ibn al-A’raj he says,
انْتَهَيْتُ إِلَى ابْنِ عَبَّاسٍ رضى الله عنهما فَقُلْتُ لَهُ
أَخْبِرْنِي عَنْ صَوْمِ عَاشُورَاءَ فَقَالَ إِذَا رَأَيْتَ هِلاَلَ الْمُحَرَّمِ فَاعْدُدْ وَأَصْبِحْ يَوْمَ التَّاسِعِ صَائِمًا قُلْتُ هَكَذَا كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَصُومُهُ قَالَ نَعَمْ
I went to Ibn Abbas (may Allah blesses him) and I say,
“Tell me about fasting the day of Ashura”. Ibn Abbas says, “When you see the crescent of the month of al-Muharram, count the days and wake up to fast on the ninth day”. I say, “Is this how the Messenger of Allah ﷺ fasted it?” Ibn Abbas says, “Yes” [Saheeh Muslim].
An-Nawawi says, “Al-Shafi’i and his companions, Ahmad, Ishaq, and others say it is recommended to fast the ninth and tenth of al-Muharram together, as the Prophet ﷺ fasts the tenth and intended to fast the ninth.” [Sharh al-Nawawi ‘alá Saheeh Muslim].
So, let’s fast at 9th and 10th Muharram!
Read also: The Month Of Ramadan Is Full Of Virtues
InshaAllah tomorrow is the 9th of al-Muharram. Donate $5 now to: ussunnah.org/orphan