SB 6.4.5

drumebhyaḥ krudhyamānās te
 tapo-dīpita-manyavaḥ
mukhato vāyum agniṁ ca
 sasṛjus tad-didhakṣayā
Synonyms: 
drumebhyaḥ — unto the trees; krudhyamānāḥ — being very angry; te — they (the ten sons of Prācīnabarhi); tapaḥ-dīpita-manyavaḥ — whose anger was inflamed because of long austerities; mukhataḥ — from the mouth; vāyum — wind; agnim — fire; ca — and; sasṛjuḥ — they created; tat — those forests; didhakṣayā — with the desire to burn.
Translation: 
Because of having undergone long austerities in the water, the Pracetās were very angry at the trees. Desiring to burn them to ashes, they generated wind and fire from their mouths.
Purport: 

Here the word tapo-dīpita-manyavaḥ indicates that persons who have undergone severe austerity (tapasya) are endowed with great mystic power, as evinced by the Pracetās, who created fire and wind from their mouths. Although devotees undergo severe tapasya, however, they are vimanyavaḥ, sādhavaḥ, which means that they are never angry. They are always decorated with good qualities. Bhāgavatam (3.25.21) states:

titikṣavaḥ kāruṇikāḥ
 suhṛdaḥ sarva-dehinām
ajāta-śatravaḥ śāntāḥ
 sādhavaḥ sādhu-bhūṣaṇāḥ

A sādhu, a devotee, is never angry. Actually the real feature of devotees who undergo tapasya, austerity, is forgiveness. Although a Vaiṣṇava has sufficient power in tapasya, he does not become angry when put into difficulty. If one undergoes tapasya but does not become a Vaiṣṇava, however, one does not develop good qualities. For example, Hiraṇyakaśipu and Rāvaṇa also performed great austerities, but they did so to demonstrate their demoniac tendencies. Vaiṣṇavas must meet many opponents while preaching the glories of the Lord, but Śrī Caitanya Mahāprabhu recommends that they not become angry while preaching. Lord Caitanya Mahāprabhu has given this formula: tṛṇād api sunīcena taror api sahiṣṇunā/ amāninā mānadena kīrtanīyaḥ sadā hariḥ. “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.