Sahih Al Bukhari Volume 2 Belief. Hadith number 7.

Narrated by Ibn 'Umar Razi ALLAH Tala Anhu
Allah's Apostle said: Islam is based on (the following) five (principles): 1. To testify that none has the right to be worshipped but Allah and Muhammad is Allah's Apostle. 2. To offer the (compulsory congregational) prayers dutifully and perfectly. 3. To pay Zakat (i.e. obligatory charity) . 4. To perform Hajj. (i.e. Pilgrimage to Mecca) 5. To observe fast during the month of Ramadan.
This hadith is narrated by Ibn 'Umar Razi ALLAH Tala Anhu, one of the companions of the Prophet Muhammad (Peace Be Upon Him). The five pillars of Islam are the fundamental acts of worship and obedience that every Muslim is required to observe. They are as follows:

Shahada (Testimony of Faith): This is the declaration that there is no god worthy of worship except Allah, and Muhammad is His messenger. It is the central creed of Islam.

Salah (Prayer): Muslims are required to perform five daily prayers facing the Kaaba in Mecca. These prayers are a direct link between the worshipper and Allah and serve as a reminder of the importance of spirituality in daily life.

Zakat (Charity): Muslims are obligated to give a portion of their wealth to those in need. It is a form of almsgiving and is intended to help alleviate poverty and establish economic equality.

Hajj (Pilgrimage): Muslims who are physically and financially able are required to perform the pilgrimage to Mecca at least once in their lifetime. Hajj occurs during the Islamic month of Dhu al-Hijjah and involves a series of rituals.

Sawm (Fasting during Ramadan): Muslims fast from dawn to sunset during the month of Ramadan. This includes abstaining from food, drink, and sinful behavior. Fasting during Ramadan is a means of self-discipline, self-reflection, and spiritual growth.

These five pillars serve as the foundation of a Muslim's faith and practice, providing a framework for a believer's relationship with Allah and with others in the community.