Ishavasya Deepika by Sri Shankarananda -

The Ishavasya is an Upanishad under the Shukla Yajurveda branch. Among the ten major Upanishads, this Upanishad occupies a very important place. It contains only 18 mantras. It has no fiction. From the first mantra of this Upanishad, "Ishavasyamidansarvanyatkinch jagatyam-jagat..." to the eighteenth mantra, "Agne naya supatha raye asman vidhvani deva vayunani vidvan..." the mystery of knowledge, worship and action is described.