פירוש על ברכות 44:17

THE SACRIFICE OF THE WICKED IS AN ABOMINATION. When Raboh said that when one finds excrement in the area where he was praying, even though he sinned by not checking out in advance that it was free of excrement, his prayer is still a prayer. Rovo asks: but we have learned (Mishlay 21, 27) the sacrifice of the wicked is an abomination. The Gemara’s question seems to encompass any situation where one found excrement where he prayed. R’I tells us that this is not so. R’I says that his prayer is an abomination only in a place where he should have had a doubt and assumed that there is excrement¹See Rosh Simon 22, where he cites Rabainu Yonoh who says that this can be seen from the Gemara earlier. When discussing one who discovered excrement while praying, the Braiso says that he should move to a position where the excrement is behind him or to his side. The Braiso does not say that he must repeat his prayers. This must be because the Braiso is discussing a place where one need not consider the likelihood of finding excrement. The dispute between Raboh and Rovo is speaking where the likelihood of finding excrement should be considered. in that place. Otherwise his prayer is not an abomination and he certainly need not pray again.

ALTHOUGH HE PRAYED, HIS PRAYER IS AN ABOMINATION. What is the ruling in this case where the prayer is deemed an abomination? And it is a “twisted thing that cannot be straightened” (Koheles 1, 15), in other words he cannot recite the prayer again. He therefore cannot correct the “twisted thing”. And R’I says that he should repeat the prayer once again.¹Most poskim accept this onion including the Shulchan Aruch Orac Chaim 76, 8.

Some edd. add: "What remedy is there? Let him repeat the Tefillah"; but this is probably a marginal gloss which was incorrectly incorporated in the text.