Ibn 'Umar said, "The Prophet (ﷺ) used to make his she-camel sit across and he would offer (prayer) facing it (as a Sutra). I asked, "What would the Prophet (ﷺ) do if the she-camel was provoked and moved?" He said, "He would take its camel-saddle and put it in front of him and offer (prayer) facing its back part (as a Sutra). And Ibn 'Umar used to do the same." [This indicates that one should not offer (prayer) except behind a Sutra]. [1:485-O.B.]