If objective moral values and duties does not exist, God does not exist. Objective moral values and duties does exist, therefore, God exists. - William Lane Craig
To argue for moral values and duties to be subjective (changeable based on time, event, people, place, etc.) is to, at the same time, argue that God/good does not exist.
The law and the prophets explicitly claims that morality is objective[1], and that God/good is immutable[2]. It also, explicitly, calls the profaning of the seventh day, the transgression of the fourth commandment, evil[3].
Therefore, to write/interpret any writings to mean that we can profane the Sabbath and maintain that this writing/interpretation is infallibly true, the author/interpreter has no choice but to, at the same time, discredit the law and the prophets as false/inaccurate.
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[1]
Deut 30:15-16,19; Is 5:20,24; 8:19-20
[2]
Mal 3:6
[3]
Ex 16:27-28; Neh 13:17-18; Is 56:2; Eze 22:26
[4]
Gen 2:2-3; Ex 20:11