(a) It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) was asked about dough into which drops of blood had fallen, and the Prophet (peace and blessings be upon him) forbade eating it.
(b) It is narrated from Sayyiduna Anas (may Allah be pleased with him) that a slave girl kneaded dough in a vessel and her hand was wounded, because of which drops of blood fell into the dough. She asked the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "Do not eat it."
Suwayd confused the narration of this hadith, narrating it once from Nuh from al-Hasan and once from Humayd from Anas; most of his hadith are not corroborated by trustworthy narrators, and he is da'if (weak), as Ahmad bin Hanbal, Yahya bin Ma'in and other imams described him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1116