وَالْخَبَرُ الصَّادِقُ أَيِ الْمُطَابِقُ لِلْوَاقِعِ
A truthful report is one that corresponds to reality.
Correspondence concerns what the report affirms or denies. If someone says, “Zayd is at home,” the report is true when he is there and false when he is not. The actual state of affairs supplies the standard of assessment.
Good intention is not sufficient for truth: a sincere speaker may nevertheless be mistaken. Neither does the hearer's confidence determine whether the statement is actually true. We must distinguish the objective correspondence of the claim from both the speaker's sincerity and the audience's psychological reaction.