Sa'id bin al-As (may Allah be pleased with him) asked Abu Musa and Hudhayfah (may Allah be pleased with them both): How did the Messenger of Allah (peace and blessings be upon him) say the takbirs in Eid al-Fitr and Eid al-Adha? Abu Musa (may Allah be pleased with him) said: As he (peace and blessings be upon him) used to say four takbirs over funerals. And Hudhayfah (may Allah be pleased with him) said: Abu Musa has spoken the truth. He said: That is how I used to say the takbirs in Basrah, when I was there.
The narrator of this hadith has been contradicted in two places: one is in attributing it to the Prophet (peace and blessings be upon him), and the other is in the answer of Abu Musa. What is well known in this story is that they referred their matter to Ibn Mas'ud, and Ibn Mas'ud gave him a ruling to that effect, without attributing it to the Prophet (peace and blessings be upon him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6183
Sa'id bin al-As (may Allah be pleased with him) came before Eid al-Adha and sent a man to Abdullah bin Mas'ud, Abu Musa and Abu Mas'ud al-Ansari (may Allah be pleased with them) to ask them about the takbirs. They left the decision to Abdullah bin Mas'ud (may Allah be pleased with him).
Then Abdullah bin Mas'ud (may Allah be pleased with him) said: Say four takbirs, then recite, then bow with the fifth takbir; then stand and recite, then say four takbirs and bow with the fourth takbir.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6184
Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: In the two Eids there are five takbirs in the first rak'ah and four takbirs in the second rak'ah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6185