The bull symbolizes dharma.

In Hindu philosophy, the bull (known as Vrishabha or Nandi) symbolizes Dharma, representing its stability on four “legs,” which are the four essential virtues of austerity (Tapas), cleanliness (Shaucha), mercy (Daya), and truthfulness (Satya). These principles are considered the foundational pillars of righteous living, and their decline, especially in later eras (Yugas), is seen as a weakening of Dharma itself. 

The Four Pillars of Dharma

• Satya (Truthfulness):Adherence to truth and integrity. 
• Daya (Mercy/Compassion):Kindness and compassion for others. 
• Shaucha (Cleanliness):Purity of both body and mind. 
• Tapas (Austerity):Self-discipline, hard work, or dedication.