Isha - 16-pūṣann ekarṣe yama

Commentary by Sri Adi Sankaracharya – Translated in English

‘Pushan,’ vocative case meaning ‘O Sun.’ The Sun is called Pushan because he feeds the world. ‘Ekarshi’ means ‘one who travels alone.’ The Sun is called Vania, because he controls all. He is called Surya because he imbibes Prana, rays and liquids. ‘Prajapatya’ means ‘son of Prajapati.’ ‘Vyuha’ means ‘remove to a distance thy rays.’ ‘Samuha,’ means ‘gather up, i.e., contract.’ ‘Tejah’ means. ‘burning light.’ I wish to behold by thy grace thy most glorious form. Moreover I do not entreat thee like a servant. I am he the Parasha within the solar orb. composed of Vyakritis as limbs or parts. ‘Purusha’ because he has the figure of a man or because he pervades the whole in the form of Prana and intelligence or because he occupies the city (of the Soul) i.e.,

Commentary by Swami Sivananda

Verses 15 – 18 have little connection with the previous verses. These are a dying man’s prayers, added at the end. The four last Mantras 15-18 do not give a description of the nature of the Knowledge of the Self. Pushan is vocation is vocative case. It means ‘O sun!’ The Sun nourishes the world. So He is called Pushan. Ekarshi means ‘O who travels alone’. Sohamasmi-here the identity of Jiva and Brahman is established. Purusha-because He pervades everything or He occupies the city of Brahman, i.e., body.

Links
Commentary on the Isavasya Upanishad by Swami Krishnananda – Divine Life Society
Upanishad Series – Isavasya Upanishad Commentary by Swami Chinmayananda
Commentary on the Isavasya Upanishad by Paramarthananda