It does so because the Decalogue expresses the fundamental duties of man towards God and towards his neighbor.
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Paragraph 2072
2072. Since they express man's fundamental duties towards God and towards his neighbor, the Ten Commandments reveal, in their primordial content, grave obligations. They are fundamentally immutable, and they oblige always and everywhere. No one can dispense from them. the Ten Commandments are engraved by God in the human heart.
Paragraph 2073
2073. Obedience to the Commandments also implies obligations in matter which is, in itself, light. Thus abusive language is forbidden by the fifth commandment, but would be a grave offense only as a result of circumstances or the offender's intention. "Apart from me you can do nothing"
Paragraph 2081
2081. The Ten Commandments, in their fundamental content, state grave obligations. However, obedience to these precepts also implies obligations in matter which is, in itself, light.
Acesse nossos estudos biblicos:
How does Ruth’s story teach us about integrity and honesty?
What is the criticism against relying on military force instead of God in Amos 2:14-16?
What are Deuteronomy’s teachings on gratitude to God?
What is Ezekiel’s message about individual responsibility before God?