Saying · 10 Muharram, 2 AH
Whoever ate breakfast in the morning, let him not eat anything for the rest of the day. Today is going to be wajib to fast.
~2 AH (from Muharram through Ramadan) · 2 AH
The core acts of Islamic worship were made law within the first two years after the Hijrah. In the first Ramadan in Madinah, fasting was not yet obligatory. Then, on the 10th of Muharram in 2 AH, the Prophet ﷺ made the fast of that day, Ashura, obligatory (wajib). It was a single day's fast, a first step to accustom the Muslims to fasting.
In the Ramadan of that same year, Allah revealed the verse of Surah al-Baqarah that made the whole month of Ramadan obligatory to fast (Qur'an 2:185). From then on, the fast of the 10th of Muharram became sunnah (recommended) rather than obligatory.
Zakat followed the same gradual path. In that same Ramadan, Zakat al-Fitr, a small charity given at the end of the fast, became obligatory. A few months later in the same year came Zakat al-Mal, 2.5% of a person's wealth.
The rulings of the prayer (salah) were also completed in this period. In Makkah every prayer had been two units (rak'ahs). In Madinah, Zuhr, Asr and Isha were lengthened to four units and Maghrib to three. The rules of purification, wudu (washing before prayer) and ghusl (the full ritual bath) also came down in these first two years.
Other events recorded in 2 AH. Their order within the year is not established; use the storyline above for the sequence.
Whoever ate breakfast in the morning, let him not eat anything for the rest of the day. Today is going to be wajib to fast.