Srimad Bhagavatam Canto 03, Chapter 14, Text 25

SB 3.14.25

 devas tribhih pasyati devaras te
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Lord Siva’s body is reddish, and he is unstained, but he is covered with ashes. His hair is dusty from the whirlwind dust of the burning crematorium. He is the younger brother of your husband, and he sees with his three eyes.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Lord Siva is not an ordinary living entity, nor is he in the category of Visnu, or the Supreme Personality of Godhead. He is far more powerful than any living entity up to the standard of Brahma, yet he is not on an equal level with Visnu. Since he is almost like Lord Visnu, Siva can see past, present and future. One of his eyes is like the sun, another is like the moon, and his third eye, which is between his eyebrows, is like fire. He can generate fire from his middle eye, and he is able to vanquish any powerful living entity, including Brahma, yet he does not live pompously in a nice house, etc., nor does he possess any material properties, although he is master of the material world. He lives mostly in the crematorium, where dead bodies are burnt, and the whirlwind dust of the crematorium is his bodily dress. He is unstained by material contamination. Kasyapa took him as his younger brother because the youngest sister of Diti (Kasyapa’s wife) was married to Lord Siva. The husband of one’s sister is considered one’s brother. By that social relationship, Lord Siva happened to be the younger brother of Kasyapa. Kasyapa warned his wife that because Lord Siva would see their sex indulgence, the time was not appropriate. Diti might argue that they would enjoy sex life in a private place, but Kasyapa reminded her that Lord Siva has three eyes, called the sun, moon and fire, and one cannot escape his vigilance any more than one can escape Visnu. Although seen by the police, a criminal is sometimes not immediately punished; the police wait for the proper time to apprehend him. The forbidden time for sexual intercourse would be noted by Lord Siva, and Diti would meet with proper punishment by giving birth to a child of ghostly character or a godless impersonalist. Kasyapa foresaw this, and thus he warned his wife Diti.
Srimad Bhagavatam Canto 03, Chapter 14, Text 24
Srimad Bhagavatam Canto 03, Chapter 14, Text 26