The Isavasya Upanishad which has 18 mantras is, strictly speaking, not an Upanishad. It comes under the Samhita portion of the Sukla Yajurveda, called Vajasaneya Samhita, as the concluding 40th chapter. But since it teaches about the Supreme Brahman, it is called an Upanishad. It is in the form of a directive from a teacher to a disciple, giving the realities — tattva, hita and purushartha — following the sequence of the Brahmasutra, elaborated M.K. Srinivasan in a discourse.
This Upanishad tells us about the Supreme Brahman, the means to attain Him and the fruits of attaining Him. In other words, it talks about tattva, hita and purushartha. Vedanta Desika has commented only on this Upanishad, because it represents the Visishtadvaita philosophy fully. The Isavasyopanishad begins by saying that this world belongs to the Supreme One and that we must enjoy it with detachment. The first mantra indicates that the Supreme One is different from jivas and matter.
The words ‘idam sarvam’ indicate that both sentient and non sentient entities are real. The words ‘yat kincha’ indicate that everything has Him as the inner self. In other words, He is Omnipresent.
Lord Narayana does not move and yet He is faster than the wind. What this seemingly contradictory statement means is that the Lord, being all pervading, is present everywhere. So where is the need for Him to move anywhere? And yet, it is not that He is without the capacity to move if He so chooses. Nothing is beyond His capacity. He is both Omnipotent and Omniscient. He is far away and yet close by, says the Upanishad. He is close to those whose minds are focused on Him. But He is far away from those who are attached to objects enjoyed by the senses.
