How can God be ONE, yet three? (ECHAD אחד)
The word for ONE is ECHAD אחד in Hebrew. The word for ONE is ECHAD in Hebrew, and this is very significant because it actually implies a composite 'unity', 'being one' or 'together'.
One of the first places where the word ECHAD is used is when God created man and woman and they were BESAR ECHAD, i.e. joined together, meaning they became flesh.
We also read in the story of the Exodus from Egypt: "In a house (BAIT ECHAD) they shall eat it (the Passover lamb offering)" (Exodus 12:46).
The word ECHAD also appears in the story of the Tower of Babel. The people were ECHAD; they were ONE nation עם אחד (em echad) with ONE language.
When the spies returned from the promised land, they brought with them an ECHAD of grapes, i.e. a huge cluster or compound bunch of grapes.
God is ECHAD. God is THREE but ONE, just as man and woman become one when they become intimate. They are one in purpose and one in mission. It is a mystery, but the Word clearly permits it and Scripture points to it. FATHER, SON and HOLY SPIRIT are one. YESHUA says in John 10 "I and the Father are one".