Using Name of Father or Mother in Prayer

Question

I've noticed that when we daven for someone, sometimes we use their name as ploni ben/bat their mother's name and sometimes we refer to them as ploni ben/bat their father's name. Does anyone know when and why we sometimes do one or the other?

Answer 1

I heard from Rabbi Menachem Nissel, a noted authority on Tefillah, the following distinction:

When we are asking for rachamim (mercy - healing, shidduchim, livelihood) we use the mother's name.

When we are talking about chashivus (importance - aliyah to the Torah, dedication, general use) we use the father's name.

Additionally, the father's name is used with a deceased individual.

Answer 2

The gemara says in Nidah 31a that the father contributes the white part of the person such as bones and the mother contributes the red part such as flesh.

Therefore if we are praying for an ill person we mention the mother's name as the flesh is ill, if we pray for the deceased we mention the father's name as only the skeleton is left.