drumebhyah krudhyamanas te
mukhato vayum agnim ca
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Because of having undergone long austerities in the water, the Pracetas were very angry at the trees. Desiring to burn them to ashes, they generated wind and fire from their mouths.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Here the word tapo-dipita-manyavah indicates that persons who have undergone severe austerity (tapasya) are endowed with great mystic power, as evinced by the Pracetas, who created fire and wind from their mouths. Although devotees undergo severe tapasya, however, they are vimanyavah, sadhavah, which means that they are never angry. They are always decorated with good qualities. Bhagavatam (3.25.21) states:
A sadhu, a devotee, is never angry. Actually the real feature of devotees who undergo tapasya, austerity, is forgiveness. Although a Vaisnava has sufficient power in tapasya, he does not become angry when put into difficulty. If one undergoes tapasya but does not become a Vaisnava, however, one does not develop good qualities. For example, Hiranyakasipu and Ravana also performed great austerities, but they did so to demonstrate their demoniac tendencies. Vaisnavas must meet many opponents while preaching the glories of the Lord, but Sri Caitanya Mahaprabhu recommends that they not become angry while preaching. Lord Caitanya Mahaprabhu has given this formula: trnad api sunicena taror api sahisnuna/ amanina manadena kirtaniyah sada harih. “One should chant the holy name of the Lord in a humble state of mind, thinking oneself lower than the straw in the street; one should be more tolerant than a tree, devoid of all sense of false prestige and should be ready to offer all respect to others. In such a state of mind one can chant the holy name of the Lord constantly.” Those engaged in preaching the glories of the Lord should be humbler than grass and more tolerant than a tree; then they can preach the glories of the Lord without difficulty.