Is it obligatory to repeat the prayer after discovering traces of feces in the underwear, and is it permissible to combine the intention of Tawaf al-Ifadah with Tawaf al-Wada' after discovering traces of feces in the underwear after completing Tawaf al-Ifadah?

Whoever prays with impurity, not knowing about it, or knowing about it and forgetting to remove it, his prayer is valid according to the majority of scholars. This is the more preponderant view according to Sheikh al-Islam Ibn Taymiyyah. The Malikis hold that it is recommended to repeat the prayer if one discovers the impurity before the time for that prayer expires. There is no obligation to repeat the circumambulation (Tawaf) for someone who circumambulated the Kaaba with impurity, either out of ignorance or forgetfulness. The validity of Tawaf in this matter is more certain than the validity of prayer, because the condition of purity for Tawaf is a matter of scholarly disagreement. As for someone who performs Tawaf al-Wada' (Farewell Tawaf) with the intention of both farewell and 'Ifadah (the main Tawaf), his Tawaf is valid and sufficient for both.