إِنَّ الصِّدْقَ طُمَأْنِينَةٌ وَإِنَّ الْكَذِبَ رِيبَةٌ
Translation: Truthfulness brings reassurance, while falsehood brings doubt and unease.
Source: أحمد والترمذي
A truthful person generally does not need to keep revising or hiding a story. Falsehood can generate further fear of discovery and the temptation to add more lies. The report captures this moral contrast using طُمَأْنِينَةٌ (reassurance) and رِيبَةٌ (doubt or unease).
الصِّدْقَ and الْكَذِبَ are each nouns governed by إِنَّ, while طُمَأْنِينَةٌ and رِيبَةٌ are their corresponding predicates.
This is ethical guidance, not a test for identifying liars from anxiety or confidence alone.