KATHOPNISHAD CHAPTER 4 SHLOK 9

                                                            यतश्चोदेति सूर्योऽस्तं

                                                               यत्र च गच्छति ।

                                                             तं देवाः सर्वेऽर्पिता

                                                      स्तदुनात्येति कश्चन । एतद्वैतत् ॥ ९

                                                   YATAH CH UDETI  SURYO  

                                               ASTAM YATRA CH GACHHATI |

                                                 TAM DEVAH SAREARPITAS

                                TADU NA ARPETI KASCHAN ||ETAD VAI TAD ||9

                    THE SUN SETS 'THERE'' AND THE SUN RISES FROM 'THERE'

(THE FORCRE THAT CAUSES THE SUN TO RISE AND SET)THE GODS WORSHIP

             NOONE GOES  BEYOND  THAT AND THAT IS VERILY THAT ||9

      This Shlok is describing the ultimate Entity ? or the power behind everything. In the universe  things seem to go smoothly . The 2 heavenly bodies don't collide  and they continue to move in a path that we 'think' is determined by force called gravity . we also see at microcosm -out own physical body - how wonderfully it works. Certainly scientist will have explanation for everything with 'terms' that really do not explain but  they just give a name. The gravity which is suppose to attract 2 or many objects to each other, is not "attracting" to each other is "repulsive" at the beginning of the universe  and so the Big Bang happened. So we really don/t know why gravitational force there. So we are told by Yamaraj that the force or the energy behind the SUN's movement or for that matter any other object in the universe is the ultimate GOD . The Gods worship that GOD . The mention of the word God may be confusing. But one has to understand that there is 'SAGUN' God and there is 'NIRGUN' God . Sagun means one with GUNAS or qualities  and Nirguna means God without the qualities , So we have many things that we consider Gods BUT THEY ARE NOT THE ULTIMATE FORCE OR THE GOD . So the so called lower level Gods also worship the ultimate force the GOD . There is nothing beyond it.

 (I consider the Gods as more like appointments - Mayer or Governor or president - etc. These positions are powerful and are not in mortal world. And they are not supreme or ultimate and they also can be demoted. These Gods have qualities that we all have  and the PURUSHA or the ultimate GOD does not have ordinary Human qualities. IN in Hindu mythology we have seen Indra the King of the Gods behaving badly or harassing someone as he is worried that he may lose his position. So in this Shlok Yama is referring to these Gods )