Honoring promises is an important aspect of life. The story in Hinduism associated with importance of honoring promise is narrated to the Pandavas in the Vana Parva of Mahabharata. In the Mahabharata, Indra advised Pandavas to use their years of exile wisely to travel, see new places, and learn new skills and to spend time with sages and learned people. This will help them in becoming better human beings and rulers. This was once such story they heard from the learned people.
During a critical stage, King Sala had borrowed some swift horses from Sage Vamadeva for one month. But the king refused to return the horses after one month. This led to a confrontation between the king and the sage.
Full of wrath, Vamadeva killed Sala using his yogic powers.
After this tragic incident, Dala the younger brother of Sala became the king and he too refused to part with the horses.
Dala made plants to kill Vamadeva. The plan was to shoot an arrow on Vamadeva when he was unaware. But unfortunately the arrow hit the son of Dala and it killed him.
Now the royal family was left with no one continue the lineage. Seeing all this death happening around her for a few horses, wife of Dala intervened and put some sense into her husband who was blinded by greed and revenge.
He asked Vamadeva to forgive her husband. Dala was forced to return the swift horses that belonged to the rishi.
Pandavas learned from this story not to usurp things of other people if they are powerful kings. True dharma is in keeping one’s promise and honoring one’s words. King or common man both have to keep promise for dharma to flourish in society.