What are some real-life examples from the lives of the Companions, may Allah be pleased with them, that embody truthfulness and its manifestation in them?

The story of Ka'b ibn Malik's failure to join the Battle of Tabuk highlights the importance of truthfulness. He was saved by his truthfulness after the earth became constricted for him, and the revelation regarding his and his two companions' repentance was delayed. Allah then accepted their repentance and revealed verses concerning them. Similarly, the stance of the Bedouin who believed in the Prophet, peace and blessings be upon him, and asked to be killed as a martyr in the path of Allah, demonstrates how his sincerity with Allah led him to attain what he desired.