In Exodus 34 Moses is given a new set of ten commandments to replace the first.
Why is it that Christians normally follow and promote the old set rather than the new set?
God can remember pretty good - and we have nothing telling us in Ex 34 that the set of Ten was different that from Ex 20.
In fact in Deut 5 - Moses reminds Israel (40 years after Sinai) that it is the set given at Sinai with God speaking directly to Israel - that they are to remember and that were in Ex 34 as well.
Deut 5:
2 The Lord our God made a covenant with us at Horeb. 3 The Lord did not make this covenant with our fathers, but with us, all of us who are alive here today. 4 The
Lord spoke with you face to face at the mountain from the midst of the fire, 5
while I was standing between the Lord and you at that time, to declare to you the word of the Lord; for you were afraid because of the fire, and you did not go up on the mountain.
IT is clear that God only speaks with Israel face to face - in the Ex 20 event.
Deut 5:
22 “These words t
he Lord spoke to your whole assembly at the mountain from the midst of the fire, from the cloud, and from the thick darkness, with a great voice, and He added nothing more. He wrote them on two tablets of stone and gave them to me. 23 And
when you heard the voice from the midst of the darkness, while the mountain was burning with fire, you approached me, all the heads of your tribes and your elders. 24 You said, ‘Behold, the Lord our God has shown us His glory and His greatness, and
we have heard His voice from the midst of the fire; we have seen today that God speaks with mankind, yet he lives. 25 Now then, why should we die? For this great fire will consume us; if we hear the voice of the Lord our God any longer, then we will die! 26 For who
is there of humanity who has heard the voice of the living God speaking from the midst of the fire, as we
have, and lived? 27 Go near and listen to everything that the Lord our God says; then speak to us everything that the Lord our God speaks to you, and we will listen and do
it.’
28 “Now the Lord heard the sound of your words when you spoke to me, and the Lord said to me, ‘I have heard the sound of the words of this people which they have spoken to you. They have done well in all that they have spoken. 29 If only they had such a heart in them, to fear Me and keep all My commandments always, so that it would go well with them and with their sons forever! 30 Go, say to them, “Return to your tents.” 31 But as for you, stand here by Me, that I may speak to you all the commandments, the statutes,
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I still think the new tenth commandment ("Do not cook a young goat in its mother’s milk.") is a bit odd.
As we see in the summary of that in Deut 5 -- that mother's milk statement is not included in the ten ,, even 40 years later it is the words spoken in Ex 20 that are affirmed - when all Israel heard the ten.