Some excerpts from Bhagavad-Gita:

While contemplating the objects of the senses, a person develops attachment for them, and from such attachment lust develops, and from lust anger arises.

From anger, delusion arises, and from delusion bewilderment of memory. When memory is bewildered, intelligence is lost, and when intelligence is lost, one falls down again into the material pool.

A person who is not disturbed by the incessant flow of desires--that enter like rivers into the ocean which is ever being filled but is always still--can alone achieve peace, and not the man who strives to satisfy such desires.

A person who has given up all desires for sense gratification, who lives free from desires, who has given up all sense of proprietorship and is devoid of false ego--he alone can attain real peace." 

The persons of demoniac nature say, the entire cosmic manifestation is unreal, without a creator, without a supreme controller, without cause, originating from mutual conabitation due only to lust, no more than this. Accepting this vision the demoniac being deficient in spiritual intelligence having lost contact with their soul; degradedly engage in abominable activities to influence the destruction of the universe

यदा यदा हि धर्मस्य ग्लानिर्भवति भारत
अभ्युत्थानमधर्मस्य तदात्मानं सृजाम्यहम
परित्राणाय साधुनाम विनाषाय च दुष्कृताम
धर्म संस्थापनार्थाय संभवामि युगे युगे :

Whenever and wherever a decline of righteousness and predominance of unrighteousness prevails; at that time I manifest Myself personally... for protection of the devotees and the annihilation of the miscreants and to fully establish righteousness, I appear millenium after millenium.