I recently listened to a teaching from a Jewish man about what the greatest sin was in Judaism.
In Christianity I would say that not believing is the most devastating sin simply because this is what Jesus taught.
John 8:24 Therefore I said to you that you will die in your sins; for if you do not believe that I am He, you will die in your sins." NKJV
This is also linked to another text on the same theme
Luke 12:9 But he who denies Me before men will be denied before the angels of God.
10 "And anyone who speaks a word against the Son of Man, it will be forgiven him; but to him who blasphemes against the Holy Spirit, it will not be forgiven. NKJV
The Holy Spirit's ministry is to convict people of sin and draws them to Jesus ...for salvation. If you reject Him you are certainly in trouble.
But in the Old Covenant, with its 613 commands, what the greatest sin is is not taught to Christians today probably because it is not repeated in the New Testament. We are however told what the greatest commandment is ...
Matt 22:36-40 "Teacher, which is the great commandment in the law?" 37 Jesus said to him, "'You shall love the LORD your God with all your heart, with all your soul, and with all your mind.' 38 This is the first and great commandment . 39 And the second is like it: 'You shall love your neighbor as yourself.' 40 On these two commandments hang all the Law and the Prophets." NKJV
The New Testament focus is on LOVE...and this was the core of the Old Covenant as well. We were only to to do that which demonstrated LOVE.
So what then is the great sin you ask....one which almost every Rabbi would concur with? It is the FIRST commandment of the Ten
Ex 20:7 "You shall not take the name of the LORD your God in vain, for the LORD will not hold him guiltless who takes His name in vain. NKJV
So what does this mean and why is it so seriously regarded?
Well sadly like most believers I did not realise that this does not refer to 'cussing' as we have been taught. The shock comes when we realise that in the Bible the name of the Lord is NOT referring to 'God' or 'Jesus'.
The name of God in the bible is 'YHWH'...or pronounced as 'Yahweh'. God tells us His name and what it means.
Ex 3:13 Then Moses said to God, "Indeed, when I come to the children of Israel and say to them, 'The God of your fathers has sent me to you,' and they say to me, 'What is His name?' what shall I say to them?"
14 And God said to Moses, "I AM WHO I AM." And He said, "Thus you shall say to the children of Israel, 'I AM has sent me to you.'" NKJV
The meaning of this is simple...'I AM the one and only self existent one'.... the one who was and who is and who was to come.
The actual name of Jesus the Christ is not the word 'Jesus' which is merely a transliteration from the Greek and has no meaning at all in English. We must realise that until the 1600's the 'J' did not even exist as a letter in the English language.
Jesus as a child was given the Hebrew name of Yeshua...and Meshiah is not His surname but is the role He came to earth as ...i.e. as saviour of the World (specifically the Israelite world)
Matt 1:21 And she will bring forth a Son, and you shall call His name JESUS, for He will save His people from their sins." NKJV
Calling on the name of the LORD is to call on Yahweh to save us ...it is to call out 'Yehoshua' ...or as commonly abbreviated in that day ...'Yeshua'.
It is the acknowledgment that Yahweh Himself is the saviour and that He has done this through the work of Yeshua.....and that Yeshua himself IS Yahweh (the LORD) our salvation.
Now consider how one would take the Name of the LORD in vain?
Doing something in 'the name of the LORD' refers to doing something as His purported representative.....and in accordance with His instruction. This is also to claim a divine authority to require things of people. Calling on the name of the LORD in vain would include telling people that God requires them to do something contrary to what God in His word has commanded them to do.
Now consider perhaps preachers today demanding tithes from the poor and pronouncing OLD Covenant curses on God's children?.... and this when God commands specifically the Israelite people to GIVE to the POOR from their tithes. Further 'wage earners and widows' were NOT required to tithe...only those who farmed and raised produce from the land ... and pretending that therefore believers today 'should' tithe from their income is totally contradicting God's word that tithes were only to be from the farm produce of the land of Israel.
This is Yahweh's response to this heresy...
Mal 3:5 And I will come near you for judgment;
I will be a swift witness ....
Against those who exploit wage earners and widows and orphans NKJV
Isa 10:1 "Woe to those who decree unrighteous decrees,
Who write misfortune,
Which they have prescribed
2 To rob the needy of justice,
And to take what is right from the poor of My people,
That widows may be their prey,
And that they may rob the fatherless.
3 What will you do in the day of punishment,
And in the desolation which will come from afar?
NKJV
Churches and their leadership who teach that the scriptures require believers to tithe of their income as condition of membership ARE exploiting and oppressing the poor and widows ...and are surely guilty of taking the name of Yahweh in vain.