Musannaf Ibn Abi Shayba 3:2046

Hafs narrated to us, from ‘Asim, from al-Sha’bi, and from Ayyub, from Sa’id ibn Jubayr, they both said: If he prays and then departs, and he does not know how much he prayed, whether it was an even number or an odd number, then he must repeat [the prayer].