Sunan Abi Dawud 1230
سنن أبي داود#1230SahihNarrated Abdullah ibn Abbas: The Messenger of Allah (ﷺ) had a stop of seventeen days in Mecca and he shortened the prayer (i.e. prayed two rak'ahs at each time of prayer). Ibn Abbas said: He who stays seventeen days should shorten the prayer; and who stays more than that should offer complete prayer. Abu Dawud said: The other version transmitted by Ibn 'Abbas through a different chain adds: He (the Prophet) had a stop of nineteen days (in Mecca)
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Bukhari (1080)
In-book reference: 4:33