Musannaf Ibn Abi Shayba 3:3321

Waki’ narrated to us, from Makhul, from Ibrahim, and from Isma’il, from al-Sha’bi, from ‘Abdullah: That he used to say the takbir during al-Fitr and al-Adha nine times, nine times: five in the first [rak'ah] and four in the last. And he would recite the two recitations consecutively.