types of blood whose impurity is disputed, such as the blood of fish. Since consensus upon this unqualified claim has not been established, it is invalid to cite it as proof in matters of disagreement. Rather, one must refer back to the textual evidence. The evidence only establishes the impurity of menstrual blood; everything else remains subject to the original ruling agreed upon by both sides of the dispute—namely, ritual purity—and nothing may be excluded from it except on the basis of evidence that constitutes proof.

The other point is that those who maintain the impurity of blood have no proof other than its prohibition in the text of the Quran. They inferred impurity from prohibition, exactly as they did in the case of wine. Yet it is clear that prohibition does not necessarily entail impurity, though the converse is true, as al-Ṣanʿānī explained in Subul al-Salām, followed by al-Shawkānī and others. For this reason, the verifying scholar Ṣiddīq Ḥasan Khān said in al-Rawḍah al-Nadiyyah (1/18), after citing the aforementioned hadith of Asmāʾ and the third hadith of Umm Qays:

“Commanding that menstrual blood be washed and scraped with a rib bone establishes its impurity. The differing methods of purifying it do not remove it from being impure. As for other types of blood, the evidences concerning them are conflicting and unsettled, while the original presumption of freedom from liability remains in force until clear evidence comes that is free from any preponderating or equivalent counter-evidence. Had there been proof that the pronoun in His Most High’s saying, ‘For indeed it is impure,’ referred to everything mentioned previously in the noble verse—carrion, shed blood, and the flesh of swine—it would establish the impurity of shed blood and carrion. But nothing has been transmitted to establish this. Rather, the dispute concerns whether it refers to all of them or to the nearest antecedent; and the apparent view is that it refers to the nearest antecedent, namely the flesh of swine, due to the pronoun’s being singular. Therefore, we decisively hold here that the flesh of swine is impure, unlike blood that is not menstrual blood. Whoever seeks a thorough investigation of the disagreement concerning a pronoun such as the one mentioned in the verse should refer to what the scholars of legal theory have said regarding a qualification that occurs after a sentence containing several matters.”

For this reason, al-Shawkānī did not mention blood in general among the impure substances in al-Durar al-Bahiyyah; rather, he mentioned only menstrual blood. Ṣiddīq Ḥasan Khān followed him in this, as you have seen from what I quoted from him