Sunan Abi Dawud 9
سنن أبي داود#9SahihNarrated Abu Ayyub :That he (the Holy Prophet, sal Allahu alayhi wa sallam) said:"When you go to the privy, neither turn your face nor your back towards the qiblah at the time of excretion or urination, but turn towards the east or the west. (Abu Ayyub said): When we came to Syria, we found that the toilets already built there were facing the qiblah, We turned our faces away from them and begged pardon of Allaah
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 (394) Sahih Muslim (264)
In-book reference: 1:9