The Literal Commandment
Hear, O Israel! The LORD is our God, the LORD is one! (Deuteronomy 6:4)
The word translated into English as LORD is the special name of G-d (transliterated into English as YHVH). He is our G-d and He is One G-d... not two, three, ten, or more. He is One.
Messiah Says
Messiah confirms the commandment to know that G-d is One. He knew it and taught others the same:
Do not call anyone on earth your father; for One is your Father, He who is in heaven. (Matthew 23:9)
There are not multiple gods... there is only One.
Pictures of Messiah
This commandments pictures not only the one-ness of G-d but pictures the unity of Messiah in G-d as He declared:
"I and the Father are one." (John 10:30)
The unbelieving Jews present knew He was equating Himself with G-d because they took up stones to stone Him (verse 31) and plainly state their charge against Him (verse 33): "You, being a man, make yourself out to be G-d".
How Messiah Fulfilled
Messiah fulfilled this commandment by knowing it and teaching it to others as well.
He declared "Hear, O Israel! The LORD our G-d is One LORD." (Mark 12:29) as part of the greatest commandment.
Traditional Observance
Traditional observance of this commandment is focused on the singularly unique nature of G-d: there is only One true G-d. He is not two, three, ten, or twenty... He is one.
Other Notes
We are able to fulfill this commandment today and we should know that G-d is One, a complete Unity.
A literal reading
A literal reading of the Hebrew of Deuteronomy 6:4 reveals this: "Hear, Israel, YHVH our G-d, YHVH [is] one." [YHVH being the four-letter name of G-d given to Moses that is usually translated into English Bibles as "LORD" (all caps)].
The Hebrew word translated as "one" [echad] means a unity. It generally does not mean a singularity.
A singularity means there is only one of something. For example, the painting "Mona Lisa" by DaVinci is a singularity: there is only one. There may be many copies but there is only one original painting.
A unity means one of a group of things. For example, a single baseball team is made up of many players, managers, trainers, etc. A cluster of grapes is a single object made up of many individual grapes.
This Hebrew word, echad, is used to describe the unity of a husband and wife in Genesis:
For this reason a man shall leave his father and his mother, and be joined to his wife; and they shall become one [echad] flesh. (Genesis 2:24)
G-d's presence was in a burning bush before Moses (Exodus 3:2-4).
G-d's presence was a pillar of cloud by day and a pillar of fire by night before Israel (Exodus 13:21).
G-d's presence was in the form of a man: Yeshua, the Messiah.
John 1 tells us that the Word of G-d is G-d and became flesh and dwelt among men.
The Shema
Deuteronomy 6:4 begins with the Hebrew phrase "Shema, Yisrael" [Hear, o Israel] from which this passage derives its name: The Shema.
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