According to Srila Jiva Gosvami, the fire of pranayama is mental satisfaction. That fire was perceived by the Supersoul, Visnu, and thereby Lord Brahma and Siva also perceived it

Expressions researched:
"According to Śrīla Jīva Gosvāmī, the fire of prāṇāyāma is mental satisfaction. That fire was perceived by the Supersoul, Viṣṇu, and thereby Lord Brahmā and Śiva also perceived it"

Srimad-Bhagavatam

SB Canto 4

According to Śrīla Jīva Gosvāmī, the fire of prāṇāyāma is mental satisfaction. That fire was perceived by the Supersoul, Viṣṇu, and thereby Lord Brahmā and Śiva also perceived it. Atri Muni, by his breathing exercise, concentrated on the Supersoul, or the Lord of the universe. As confirmed in Bhagavad-gītā, the Lord of the universe is Vāsudeva (vāsudevaḥ sarvam iti (BG 7.19)), and, by the direction of Vāsudeva, Lord Brahmā and Lord Śiva workc.

SB 4.1.21, Translation and Purport

While Atri Muni was engaged in these severe austerities, a blazing fire came out of his head by virtue of his breathing exercise, and that fire was seen by the three principal deities of the three worlds.

According to Śrīla Jīva Gosvāmī, the fire of prāṇāyāma is mental satisfaction. That fire was perceived by the Supersoul, Viṣṇu, and thereby Lord Brahmā and Śiva also perceived it. Atri Muni, by his breathing exercise, concentrated on the Supersoul, or the Lord of the universe. As confirmed in Bhagavad-gītā, the Lord of the universe is Vāsudeva (vāsudevaḥ sarvam iti (BG 7.19)), and, by the direction of Vāsudeva, Lord Brahmā and Lord Śiva work. Therefore, on the direction of Vāsudeva, both Lord Brahmā and Lord Śiva perceived the severe penance adopted by Atri Muni, and thus they were pleased to come down, as stated in the next verse.