When the Sefirot are presented in the Tanya (the classic text from the first Lubavitcher Rebbe) they are called 3 Mothers and 7 Doubles. The 3 Mothers refer to the three higher Sefirot. The Seven Doubles refer to the seven lower Sefirot.
However, the original source of the terms Three Mothers and Seven Doubles is the Sefer Yetzirah, where the 22 Hebrew Letters are presented as three groups - 3 Mothers, 7 Doubles and 12 Simples.
In this picture I joined both together and placed א in Keter (Crown), מ in Chochmah (Wisdom) and ש in Binah (Understanding) - these… more