Sayyiduna Abdullah (may Allah be pleased with him) said: You have been commanded to establish four things: "Establish the prayer, give the zakah, and establish Hajj and Umrah at the House. Hajj is the greater pilgrimage (al-hajj al-akbar), and Umrah is the lesser pilgrimage (al-hajj al-asghar)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8768