4-Four is a recurrent number in both exoteric and esoteric Jewish traditions. The Passover Seder isparticularly structured around fours: the Four Questions, the Four Sons, and four cups of wine. There are four cardinal directions and there are four Matriarchs. Four is also a common factor in esoteric interpretations: four angels surround the Throne of Glory, there are four kingdoms of the eschaton, and the famous four Sages who enter Paradise.
The number 4 derives its meaning from creation. On the fourth day of what is called 'creation week' God completed the material universe. On this day he brought into existence our sun, the moon, and all the stars (Genesis 1:14 - 19). Their purpose was not only to give off light, but also to divide the day from the night on earth, thus becoming a basic demarcation of time. They were also made to be a type of signal that would mark off the days, years and seasons.
In Jewish numerology (gematria), four is associated with the letter dalet which means door or opening.
Stein seemed to like the number four and later in her writing career, she had such titles for her work as Four Saints in Three Acts and Four in America.