Bais HaVaad on the Parsha, Parshas Shmini

Blood Type 

Excerpted and adapted from a shiur by Rav Moshe Zev Granek 

April 13, 2023

Do not make your souls abominable by means of any creeping thing; and you shall not make yourselves impure through them, lest you make yourselves impure through them.

Vayikra 11:43

The Chelkas Yaakov was asked if one may receive a blood transfusion from a non-Jew. He rules that it is permitted if the patient is in danger, but a transfusion from a Jew is preferable. He explains that the Rama (Y.D. 81:7) says a Jewish baby should not nurse from a non-Jew due to timtum haleiv (spiritually stopping up the heart). Since the Gemara says that milk comes from blood, the Chelkas Yaakov says receiving a transfusion can also cause timtum haleiv.

There is a basis to differ with the Chelkas Yaakov. The Darchei Moshe cites the reason for the nursing rule from the Ran (Avodah Zarah 7b in the Rif pagination) and the Rashba (Yevamos 114a): Jews have certain positive character traits, like mercy and kindness, that a nursing Jewish woman transmits to a baby, while any negative character traits a non-Jewish wet nurse possesses can also be passed on. But the Ritva (Yevamos 114a) explains differently: The nonkosher food the non-Jewish wet nurse has ingested causes timtum haleiv in the baby. The Chelkas Yaakov’s logic appears consistent with this view. But the Rashba, whose view is codified by the Rama, maintains that the timtum comes from the person, not what she ate. If so, we have no basis from the Rishonim to assume that a non-Jew’s blood causes timtum just because her milk does. Further, even the Ritva may allow a transfusion, because Rashi (Sotah 12b) explains that Moshe did not nurse from a non-Jew due to the taste of nonkosher food in the milk. The Ritva may hold that the timtum haleiv comes from this, which does not apply to blood transfusion.