When the world is overburdened by the fighting strength of kings who have no faith in God, the Lord, just to diminish the distress of the world, descends with His plenary portion. The Lord comes in His original form, with beautiful black hair. And just to expand His transcendental glories, He acts extraordinarily. No one can properly estimate how great He is.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
भूमेः सुरेतरवरूथविमर्दितायाः क्लेशव्ययाय कलया सितकृष्णकेशः । जातः करिष्यति जनानुपलक्ष्यमार्गः कर्माणि चात्ममहिमोपनिबन्धनानि
bhūmeḥ suretaravarūthavimarditāyāḥ kleśavyayāya kalayā sitakṛṣṇakeśaḥ | jātaḥ kariṣyati janānupalakṣyamārgaḥ karmāṇi cātmamahimopanibandhanāni
SB 2.7.26