Falsehood as the contrary of ṣidq

Realities Are Established: Truth, Correspondence and Essence

وَيُقَابِلُهُ الْكَذِبُ
Its opposite is kadhib, falsehood.

Here kadhib describes a report that does not correspond to reality. In ordinary speech, “lying” can also imply intentionally giving a false report; intention and factual inaccuracy should not be conflated.

If “the treasury door is open” is said while it is closed, the proposition is false. The reporter's sincerity is a further, separate question.