You may have noticed that when we call someone by his or her Hebrew name, there are two variations. For example, one can be called Yitzchok ben Avraham (Yitzchok the son of Avraham) or Yitzchok ben Sarah (Yitzchok the son of Sarah). When and why do we use each variation?

The general custom is that for a matter relating to familial affiliation,1 we use the father’s name. This is based on the verse in Numbers: “They declared their pedigrees according to their families according to their fathers' houses…”2 Indeed one's tribal affiliation and whether one is a kohen or a Levite is dependent upon one’s father. Thus, if one is getting an aliyah or signing a halachic document such as a ketubah or get, we use the father’s name.

However, when we are beseeching G‑d for someone in need (as is the case with a mi shebeirach for one who is ill), we generally use the mother’s name. There are a number of reasons for this.

Precedent

We find that when King David prayed for himself, he repeatedly referred to himself as “your servant, the son of your maid,”3 mentioning his mother, not his father. Additionally, the Talmud states that “all incantations [use] the name of the mother.”4

Preciseness

Although we are almost always sure who the father is, we are even more sure who the mother is. According to the Zohar, when praying for mercy (especially when it comes to pikuach nefesh, the saving of a life, as is the case when praying for one who is ill), we want to be as precise as possible, so we use the mother’s name.5

Less Sins

As we pray for G‑d’s mercy, we would rather invoke the mother’s name, since women usually have less sins than men. While this seems shocking at first glance, it makes perfect sense when we consider that women aren’t obligated in the mitzvah of constantly learning Torah6 or other positive time-bound mitzvahs. Therefore, they aren’t held liable for not doing these things.7

The Primary Parent

Although both man and woman (together with G‑d, of course) are partners in the creation of the child, the child is mostly formed by the mother. Physically, the child develops in the mother’s womb, and spiritually, the child’s Jewishness is dependent upon the mother. Her very thoughts during conception have more of an effect on the child than the father’s. As such, it is appropriate to invoke the mother’s name when we are praying for mercy for the child.8

The Source of Judgment

The mystics9 explain that, in general, women come from the divine attribute of binah (“understanding”), which is also the source of the attribute of gevurah (“judgment and severity”).

Now, the attribute of judgment, in its source, binah, is pure and holy without any harshness. All of the harshness that we see coming from the attribute of judgment is only how it manifests itself down here in this physical world. Therefore, when we mention the mother’s name, we are trying to arouse and evoke the attribute of binah. When we do so, all of the harshness and impurities that evolved from it fall away, allowing the person to heal from the illness.

On the other hand, once the person has passed away (aside from the fact that we do not want any connection to the attribute of judgment at all), we mention the father’s name based on the verse in Numbers quoted above.

Mother’s Mercy

While on the discussion of evoking the mother while praying, we bear in mind the mothers who themselves pray. Indeed, we find in Scripture10 that it was specifically in the merit of the tearful prayers of our matriarch Rachel that we were redeemed from the Babylonian exile. We pray that G‑d once again hear the tearful cries for mercy from our mother Rachel, take us out of this exile and finally bring healing to this world!