A household wire was cut to tap into it to provide current for another fixture. That fixture is no longer needed so I want to rejoin the wires where they were cut. Can I just re-join them with wire nuts and leave it or do they need to be inside a junction box to be up to code? The wire will be sealed up and behind the drywall.

Thanks

They MUST be spliced properly in a junction box. This box can have a blank cover on it, but it CANNOT be buried behind a wall. The cover MUST remain accessible.