Abdur Rahman bin Abi Layla narrates from Ka'b bin Ujrah (may Allah be pleased with him) that Sayyiduna Umar (may Allah be pleased with him) said: "The prayer of Eid al-Adha is two rak'ahs, the prayer of Eid al-Fitr is two rak'ahs, the Friday prayer is two rak'ahs, and the traveller's prayer is two rak'ahs - complete, not shortened."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5718