Ibrahim al-Nakha'i (may Allah have mercy on him) narrates that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) led the people in the Maghrib prayer and did not recite anything in it until he said the salam. When he had finished the prayer, someone said to him: You did not recite anything at all. Sayyiduna Umar (may Allah be pleased with him) said: I equipped a caravan bound for Syria, and I kept bringing it down from one stage to the next until I reached Syria; then I sold it, together with its saddles, its saddle-cloths and its loads. The narrator says: So Sayyiduna Umar (may Allah be pleased with him) repeated the prayer, and the people also repeated it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3981