Ibn 'Umar (May Allah be pleased with them) reported:
The Messenger of Allah ﷺ said, "(The structure of) Islam is built on five (pillars): Testification of 'La ilaha illallah' (none has the right to be worshipped but Allah), that Muhammad ﷺ is his slave and Messenger, the establishment of Salat, the payment of Zakat, the pilgrimage to the House of Allah (Ka'bah), and Saum during the month of Ramadan."

[Al-Bukhari and Muslim].

وعن ابن عمر رضي الله عنهما، أن رسول الله ﷺ قال: "بني الإسلام على خمس: شهادة أن لا إله إلا الله وأن محمدًا عبده ورسوله، إقام الصلاة، وإيتاء الزكاة، وحج البيت، وصوم رمضان" ((متفق عليه)) .