In one version of the Vamana legend, when Mahabali offered himself for Vishnu's third step, it was an act of Mahabali's devotion. Vishnu granted him a boon. Mahabali chose to revisit earth, once every year, the lands and people he previously ruled. This revisit marks the festival of Onam, as reminder of the virtuous rule and his humility in keeping his promise before Vishnu.