The Lord said: “Sattva, Rajas and Tamas are the three qualities of mind and intellect  but not of Atman. Therefore, one should control or subdue through Sattva the other two, and control Sattva by Sattva itself.
When Sattva grows in man, he attains Dharma or righteousness which takes the form of devotion to Me. Through the use of Sattvic things, Sattva develops and thence Dharma. That Dharma of matchless power which is brought on by an increase of Sattva destroys Rajas and Tamas. When both of these are destroyed, Adharma which is an outcome of Rajas and Tamas is also quickly destroyed.
The scriptures, water, men, land, time, work, birth, meditation, Mantras and purificatory ceremonies - these are the ten causes which develop or promote the Sattva Guna.Of these,what the sages praise are Sattvic, what they condemn are Rajasic.
A man ought to use and associate with only Sattvic things and persons, for the development of Sattva; thence arises Dharma from which knowledge arises and grows till the direct realisation of Atman is attained and all the causes of mundane bondage are totally annihilated.
[N.B. -Those scriptures which are Sattvic and which lead to the attainment of Brahman should be studied. Novels and worthless books should not be read. One should not use scents, wine, opium, Canabis Idica etc. He should mix with saints and not with worldly-minded people.]