SHADDAI

אֲנִי־אֵ֣ל שַׁדַּ֔י - I Am the Almighty God

Genesis 17:1—And Abram was ninety-nine years old, and God appeared to Abram, and He said to him, "I am the Almighty God; walk before Me and be perfect.

That verse is the first time in the Torah we see the Hebrew word שַׁדַּ֔י Shaddai.

In Genesis 17, God appears to 99-year-old Abram, reaffirming the covenant by changing his name to Abraham ("father of many nations") and Sarai’s to Sarah, promising them a son named Isaac despite their old age. God establishes circumcision as the physical, everlasting sign of this covenant. While blessing Ishmael, God clarifies the covenant passes through Isaac. 

El Shaddai (אֵל שַׁדַּי) is an ancient, primary name for God in the Torah, commonly translated as "Almighty God". It appears in the Torah, particularly associated with the patriarchs Abraham, Isaac, and Jacob to signify God’s power to perform supernatural acts, especially in fulfilling covenants of fruitfulness, reproduction, and inheriting the land when natural means fail. 

According to Exodus 6:3, God was known to Abraham, Isaac, and Jacob as El Shaddai, distinct from the name YHWH. Thus, Shaddai is referred to as the Patriarchal name. Other, related names used during this period include El (God), El Elyon (God Most High), and El-Elohe-Israel (God, the God of Israel). 

Almighty/Power, often understood as "God Almighty" (from shadad), implies supreme, irresistible power. The name is used in blessings (Genesis 28:3, 49:25) and when calling for protection (Genesis 43:14).

Shaddai On the Doorposts

In modern Judaism, the letter Shin (ש) on a mezuzah case is a reference to Shaddai. Shin is the 21st Hebrew letter with a numerical value of 300. 

Shaddai Numerical Value:

Shin (ש): 300

Dalet (ד): 4

Yud (י): 10 

Total Numerical Value (Shaddai): 

300 + 4 + 10=314*

* By the way, the number 314 most commonly represents the first three digits of the mathematical constant Pi.  

There is a belief that Pi is hidden in Genesis 1:1 through gematria (numerical values of Hebrew letters) and mathematical, equidistant letter sequences, often cited as a ~99.96% accurate approximation, what amounts to the first few digits-314. Proponents suggest this is a deliberate encoding representing a Divine signature in the text. 

The Gaurdian of the Doors of Israel, on the doorposts of Jewish homes, is El Shaddai. Inside a mezuzah is the Shema.