set / written / carved / etched in stone

/sˈɛt ɹˈɪtən kˈɑːvd ˈɛtʃt ɪn stˈəʊn/

/sˈɛt ɹˈɪʔn̩ kˈɑːɹvd ˈɛtʃt ɪn stˈoʊn/

not possible to be altered or changed

Examples

1. Like the commandments written in stone.

2. These proposals are for discussion, they're not carved in stone.

3. The deal isn't yet etched in stone, but we're confident it will go ahead as hoped.

4. I don't want anything feeling like it's written in stone, And we're bad, Or not good enough, If we don't get it done.