SB 5.21.3

yan-madhya-gato bhagavāṁs tapatāṁ patis tapana ātapena tri-lokīṁ pratapaty avabhāsayaty ātma-bhāsā sa eṣa udagayana-dakṣiṇāyana-vaiṣuvata-saṁjñābhir māndya-śaighrya-samānābhir gatibhir ārohaṇāvarohaṇa-samāna-sthāneṣu yathā-savanam abhipadyamāno makarādiṣu rāśiṣv aho-rātrāṇi dīrgha-hrasva-samānāni vidhatte.
Synonyms: 
yat — of which (the intermediate space); madhya-gataḥ — being situated in the middle; bhagavān — the most powerful; tapatām patiḥ — the master of those that heat the whole universe; tapanaḥ — the sun; ātapena — by heat; tri-lokīm — the three worlds; pratapati — heats; avabhāsayati — lights; ātma-bhāsā — by its own illuminating rays; saḥ — that; eṣaḥ — the sun globe; udagayana — of passing to the northern side of the equator; dakṣiṇa-ayana — of passing to the southern side of the equator; vaiṣuvata — or of passing through the equator; saṁjñābhiḥ — by different names; māndya — characterized by slowness; śaighrya — swiftness; samānābhiḥ — and by equality; gatibhiḥ — by movement; ārohaṇa — of rising; avarohaṇa — of going down; samāna — or of staying in the middle; sthāneṣu — in positions; yathā-savanam — according to the order of the Supreme Personality of Godhead; abhipadyamānaḥ — moving; makara-ādiṣu — headed by the sign Makara (Capricorn); rāśiṣu — in different signs; ahaḥ-rātrāṇi — the days and nights; dīrgha — long; hrasva — short; samānāni — equal; vidhatte — makes.
Translation: 
In the midst of that region of outer space [antarikṣa] is the most opulent sun, the king of all the planets that emanate heat, such as the moon. By the influence of its radiation, the sun heats the universe and maintains its proper order. It also gives light to help all living entities see. While passing toward the north, toward the south or through the equator, in accordance with the order of the Supreme Personality of Godhead, it is said to move slowly, swiftly or moderately. According to its movements in rising above, going beneath or passing through the equator — and correspondingly coming in touch with various signs of the zodiac, headed by Makara [Capricorn] — days and nights are short, long or equal to one another.
Purport: 

Lord Brahmā prays in his Brahma-saṁhitā (5.52):

yac cakṣur eṣa savitā sakala-grahāṇāṁ
 rājā samasta-sura-mūrtir aśeṣa-tejāḥ
yasyājñayā bhramati saṁbhṛta-kāla-cakro
 govindam ādi-puruṣaṁ tam ahaṁ bhajāmi

“I worship Govinda, the primeval Lord, the Supreme Personality of Godhead under whose control even the sun, which is considered to be the eye of the Lord, rotates within the fixed orbit of eternal time. The sun is the king of all planetary systems and has unlimited potency in heat and light.” Although the sun is described as bhagavān, the most powerful, and although it is actually the most powerful planet within the universe, it nevertheless has to carry out the order of Govinda, Kṛṣṇa. The sun-god cannot deviate even an inch from the orbit designated to him. Therefore in every sphere of life, the supreme order of the Supreme Personality of Godhead is carried out. The entire material nature carries out His orders. However, we foolishly see the activities of material nature without understanding the supreme order and Supreme Person behind them. As confirmed in Bhagavad-gītā, mayādhyakṣeṇa prakṛtiḥ: material nature carries out the orders of the Lord, and thus everything is maintained in an orderly way.