Salim bin Abdullah says: When Umar bin al-Khattab (may Allah be pleased with him) came to Makkah, he would lead them in two rak'ahs and then say: "O people of Makkah! Complete your prayer, for we are travellers."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5328