Musannaf Ibn Abi Shayba 3:3348

Ishaq ibn Mansur narrated to us, he said: Abu Kudaynah narrated to us, from al-Shaybani, from al-Sha’bi and al-Musayyab, they both said: The prayer on the two Eids is nine takbirs: five in the first [rak'ah] and four in the last. There is no takbir between the two recitations.