Abd al-Rahman bin Abi Layla narrates from a trustworthy person, who narrates from Sayyiduna Umar (may Allah be pleased with him): "The prayers of Eid al-Adha, Fitr and Friday are two rak'ahs each, and for the traveller the complete prayer is two rak'ahs, not shortened; this is according to the words of the Prophet (peace and blessings be upon him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6236