The knowledge about the GUNAS ( Saatvik, Raajasik, Taamasik) is described in the 14th Chapter of the Bhagavad Gita.
सर्वद्वारेषु देहेऽस्मिन्प्रकाश उपजायते |The Bhagavad Gita Chapter 14 Verse 11
ज्ञानं यदा तदा विद्याद्विवृद्धं सत्वमित्युत || 11||
sarva-dvāreṣhu dehe ’smin prakāśha upajāyate
jñānaṁ yadā tadā vidyād vivṛiddhaṁ sattvam ity uta
When the illumination of the knowledge of God’s Energy is perceived through the inlets and outlets of all the sense organs, it is then recognized that Sattwik Guna is dominating. Any Sense Perception, uninfluenced by Ego based reactions and actions is known as Sattwik. He feels the harmonious and joyful presence of the soul or the Spirit. He has gone beyond the ego-based fluctuations and dualities of experiences.
लोभ: प्रवृत्तिरारम्भ: कर्मणामशम: स्पृहा |
रजस्येतानि जायन्ते विवृद्धे भरतर्षभ || 12||
lobhaḥ pravṛittir ārambhaḥ karmaṇām aśhamaḥ spṛihā
rajasy etāni jāyante vivṛiddhe bharatarṣhabha
The Bhagavad Gita Chapter 14 Verse 12
Greed, restlessness, taking initiatives for actions, tension, cravings; these arise and predominate, O’ the best leader of the Bharata race when Raajas become dominant. When the Raajasik Guna dominates, there arise, greed, cravings, restless activities, giving rise to tenseness and lack of calmness and peace.
अप्रकाशोऽप्रवृत्तिश्च प्रमादो मोह एव च |
तमस्येतानि जायन्ते विवृद्धे कुरुनन्दन || 13||
aprakāśho ’pravṛittiśh cha pramādo moha eva cha
tamasy etāni jāyante vivṛiddhe kuru-nandana
The Bhagavad Gita Chapter 14 Verse 13
Lack of judgment and indiscrimination, inertness, carelessness, delusion; these originate, O’ Joy of the Kuru race when Tamasik Guna or quality becomes predominant. When Tamasik Guna or the basic quality of Mother Nature, originates and dominates; there arise, lack of judgment and indiscrimination, inertness, carelessness, and delusions. A Taamasik person possesses all these qualities. There is a lack of intellectual quality and also lack of initiatives and actions.
यदा सत्वे प्रवृद्धे तु प्रलयं याति देहभृत् |
तदोत्तमविदां लोकानमलान्प्रतिपद्यते || 14||
yadā sattve pravṛiddhe tu pralayaṁ yāti deha-bhṛit
tadottama-vidāṁ lokān amalān pratipadyateec4911
The Bhagavad Gita Chapter 14 Verse 14
If a person leaves the body at death, when, SATTWA is dominating, then the person (Spirit) migrates to the best heavens, where live Souls who have achieved the Highest. In a person, in whom Sattwik Guna or quality is dominating, and the person leaves this world at death, he migrates or his spirit proceeds to higher heaven, which is inhabited by souls (Jeevatmas) who have realized the highest knowledge. So Sattwa Guna, takes a person to the higher worlds, on way to attaining Perfection or God-realization. Dear divine friends, it is useful to maintain a calm mind under all circumstances. Only Kriya Yoga Pranayam and Meditation can give calmness of mind. If the mind is calm, it can easily observe its own workings.
It is the three Gunas, which influence thoughts. The thoughts, in turn, influence the actions. Actions bring results i.e. Karma Phal. The Karma Phal or the results of Actions is destiny or fate. It is only a calm mind, born of Pranayam and meditation, which can watch and control the functions of the 3 Gunas, which influence Actions or Karma and in turn, the Destiny. We humbly and with love, thank Lord Krishna, who kindly gave this knowledge to mankind, through Arjuna, in the Bhagavad Gita. This is for better quality and quantity of life, to overcome sufferings, and ultimately for Self Realization.
May God bless you with Love, Laughter, Light, Longevity and Life.
With Love and Best Wishes,
Paramahansa Atmananda Ji