What is the reason for Sage Atri to get burnt in fire?

[Ms. Laxmi Thrylokya asked: Sage Atri first did penance by chanting 'Om' to fulfill a (worldly) desire to attain a child. But he was burnt in fire as the result. Second time, he performed the penance to attain the vision of one God who is responsible for creation, maintenance and destruction of entire creation. God was pleased with the Sage and God not only gave the vision to him as Lord Datta but also became his son fulfilling his lost desire. Swāmi, You said earlier that worshiping formless God (OM) leads to misery. What is the actual reason for Sage Atri to get burnt in fire? Is it because of chanting 'Om'? Or is it because he asked for fulfillment of a worldly desire? -At Your Divine Lotus Feet, Laxmi Thrylokya]

Swāmi Replied: AUM indicates the unimaginable God (Nirguṇa Brahman) doing the three works of creation, maintenance and destruction of the world. AUM contains three letters linked with these three words (Tasya Vācakaḥ Praṇavaḥ– Brahmasūtram). The Gītā says that worship of unimaginable God leads to misery (Avyaktā hi Gatir Duḥkham…). The soul must worship only mediated God with whom the unimaginable God merged doing these three works. Actually, the unimaginable God alone can do these three works functioning through any medium, called as mediated God (Saguṇa Brahman). Hence AUM shall be associated with the Divine form or medium of God only like AUM Namo Brahmaṇe or AUM Namo Nārāyaṇāya or AUM Namaḥ Śivāya etc. The fire developed in the body of Atri indicates the misery told by the Gītā. Second time when Atri did penance concentrating on the first mediated unimaginable God, everything went on well.