Let us recount from different Puranas:

Once, while walking through the Daruka vana, Shiva brought trouble for all the saints who were involved in intense austerities in that forest. Shiva is far more handsome than Vishnu. For this reason He is called Sudaresha. Vishnu is not addressed as Sundaresha but as Mohanānga. It is said that Parvati is dark complexioned. None of the 33 crore Devatas can match Shiva in beauty.

The greatest saints who were meditating in Dāruka vana were fascinated by His beauty. We are talking of those saints who were of the highest calibre! They had undertaken penance for many many yugas and were masters in all forms of knowledge! Such was their penance that their matted locks touched the ground. They had totally abstained from food for long periods of time. Penance done without harming the body and without harming others is true penance.

Such saints were captivated by His beauty! Krishna’s beauty only attracted woman. But Shiva’s beauty captivated not only women but also men! For a little time these men believed that they had transformed into women and getting up from their seats they began to follow Shiva!

The wives of these saints were responsible for maintaining the holy fire within the house. It was their duty to ensure that fire eternally burned in the house without dying down. When these dutiful chaste wives saw their husbands leaving them and going along with Shiva, they cried loudly in grief.

“Hey Shiva, You may be handsome, no doubt, but You can never create such feelings of love in us as we are extremely chaste woman. Let go off our husbands for without them we cannot survive. We have given up our parental homes and are here only to dutifully serve our husbands. We have been serving our husbands devotedly for the past thousands of years. To us husband is God”.

In Krishna’s sports, the mothers of the Gopikas go and beg him to set the girls free. It sounds morally correct. But here Shiva was unaware that thousands of saints were following Him as he moved about in the forest!

As these saints walked, the many demons on the path were dying unable to withstand the intensity of their penance!

Shiva, the ever-compassionate Supreme Lord, observed the demons dying and was unhappy. He pondered over the reason. He concluded that the intensity of the penance of the saints who were following Him led to the death of these demons who were predominantly of tamasic traits. ‘Oh, a terrible calamity is about to take place. The wives of these saints are bound to curse me now’.

Even as He was thinking, Arundhati and other chaste women, who were the wives of the saints, cursed Shiva. They cursed that He should turn into a pāśāṇa or linga. With this curse He transformed into a linga. All the saints then bathed the Lord with abhishekam and decorated Him beautifully. Even to this day saints perform these rituals, and while chanting the Rudra, Namaka and Camaka, continue to call Him.

Then the saints addressed their wives and said, “Due to your curse our dear God has transformed into a linga. Please go away. Please do not come near us. We want to remain here with Him.”The wives replied, “We will stay along with you here and worship Him”.

• Shivaratri 2016

Another story:

Once, an argument ensued between Brahma and Vishnu which turned into a great dispute. With an intention of bringing about a settlement between them, Shiva entered into the scene. Absorbing both of them into Him, he took on the form of a huge, endless pillar of fire.

To figure out the origin of this pillar of fire, Lord Brahma in the form of a swan flew into space. With the same intent, Lord Vishnu in the form of varaha (wild boar) went deep into Patala (hell). No matter how far they travelled in space, neither the beginning nor the end of this pillar could be traced. No matter how much they searched, Lord Shiva could not be seen. It was then that they realized the greatness and infinity of Shiva.

At that point the ever-compassionate Lord Shiva, took on the form of a small Jyotirlinga (pillar of light, a small linga) and appeared before them. Only that idol (moorti) which manifests during Ardra nakshatra (star Betelgeuse) is considered as the Lingodbhava moorti. This is how the Lord Shiva has been referred to as the pillar of fire.

• (Bhaktimala 83,92)