It is Krishna who gave to Arjuna a number of white horses. It is he who is the creator of all horses. This world represents his car. He it is who yokes that car for setting it in motion. That car has three whcels. It has three kinds of motion. It has four horses yoked it. It has three naves.
स एव पार्थाय श्वेतमश्वं प्रायच्छत् स एवाश्वानथ सर्वांश्चकार। स्त्रिवृच्छिराश्चतुरश्वस्त्रिनाभिः॥