I saw Ibn Umar make his camel kneel facing the qiblah, then he sat down and urinated toward it. I asked, "Abu Abdul-Rahman, has this not been forbidden?"He replied, "Yes, but it was only forbidden in open ground. If there is something between you and the qiblah that screens you, there is no harm in it."
رأيت ابن عمر أناخ راحلته مستقبل القبلة، ثم جلس يبول إليها، فقلت: يا أبا عبد الرحمن! أليس قد نهي عن هذا؟ قال: بلى، إنما نهي عن ذلك في الفضاء، فإذا كان بينك وبين القبلة شيء يسترك فلا بأس.
Abu Dawud (11) reported it from Muhammad bin Yahya bin Faris, from Safwan bin Isa, from Hasan bin Zakwan, from Marwan the Fair, who mentioned it. Its chain of transmission is hasan, due to the discussion surrounding Hasan bin Zakwan, though his hadith is hasan.Ibn Khuzayma (60) and Hakim (1/154) both graded it sahih, from the route of Hasan bin Zakwan, with the same wording. Hakim said, "Sahih according to the criterion of Bukhari" (and in another copy, "according to the criterion of Muslim") "and he relied on Hasan bin Zakwan as evidence."Daraqutni (1/58) also reported it and said, "Sahih, all of its narrators are trustworthy."