(a) Jubayr bin Nufayr narrates from Ibn al-Simt that he came to a village of Hims that was thirteen miles away and prayed two rak'ahs there. I said: "You prayed two rak'ahs?" He said: "I saw Umar bin al-Khattab (may Allah be pleased with him) praying two rak'ahs at Dhul-Hulayfah. I asked him about it, and he said: 'I only do as I saw the Prophet (peace and blessings be upon him) do.'"
(b) In the narration of Abu Dawud: Ibn al-Simt heard Umar (may Allah be pleased with him) say: "I prayed two rak'ahs with the Prophet (peace and blessings be upon him) at Dhul-Hulayfah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5447