There are five essential duties that a Muslim must observe, they are called the 5 Pillars of Islam.
The Five Pillars consist of:
1. Kalimah Shahadah: To sincerely recite the declaration of faith
لَا إِلٰهَ إِلَّا الله مُحَمَّدٌ رَسُولُ الله
lā ʾilāha ʾillā-llāhu Muḥammadun rasūlu-llāh
There is no god but Allah (and) Muhammad is the messenger of Allah.
2. Salaah: To Perform the 5 daily prayers Fajr, Zohar, Asr, Maghrib & Isha
3. Zakat: To donate 2.5%, each year, of one’s unused wealth to the poor/needy
4. Sawm: To Fast, from dawn to dusk, during the month of Ramadhaan
5. Hajj: To Perform the pilgrimage to Mecca once in a lifetime.
Reference from Hadith:
On the authority of Hadhrat Umar (may Allah be pleased with him) the Messenger of Allah (peace be upon him) said:
“Islam has been built on five [pillars]: Testifying that there is no god but Allah and that Muhammad is the Messenger of Allah, establishing the prayer, paying the zakat, performing pilgrimage to the House of Allah and fasting in Ramadhan”
[Bukhari & Muslim]