كتاب الحج
10  
The Book of Hajj
(233)
Chapter: The Obligation of Hajj (Pilgrimage) and its Excellence
(233)
- باب وجوب الحج وفضله
Riyad as-Salihin 1271
Ibn 'Umar (May Allah be pleased with them) reported:
The Messenger of Allah (ﷺ) said, "(The superstructure of) Islam is based on five (pillars), testifying the fact that La ilaha illallah wa anna Muhammad-ar-Rasul-ullah [there is no true god except Allah, and Muhammad ((ﷺ)) is the Messenger of Allah], establishing As- Salat (the prayers), paying Zakat (poor due), the pilgrimage to the House [of Allah (Ka'bah)], and the Saum (fasting) during the month of Ramadan."

[Al-Bukhari and Muslim].

وعن ابن عمر رضي الله عنهما أن رسول الله صلى الله عليه وسلم قال‏:‏ بني الإسلام على خمس‏:‏ شهادة أن لا إله إلى الله وأن محمدًا رسول الله، وإقام الصلاة، وإيتاء الزكاة، وحج البيت، وصوم رمضان‏"‏ ‏(‏‏(‏متفق عليه‏)‏‏)‏
Reference : Riyad as-Salihin 1271
In-book reference : Book 10, Hadith 1