O Partha, the mentality in the mode of passion cannot distinguish between dharma and adharma, cannot discern what is right and what is wrong, and cannot decide what is duty and what is not duty.
Bhagavad Gita - Chapter 18 - Moksha Yoga - The Yoga of Supreme Perfection
O Partha, the mentality in the mode of ignorance regards that which is adharma to be dharma and that which is dharma to be adharma. It regards everything to be the opposite of reality.
O Partha, that determination by which one strictly controls the mind, life-airs and the senses through the process of yoga is in the mode of goodness.
O Partha, that determination by which one maintains a sense of dharma in order to accrue wealth and fulfill material desires is in the mode of passion.
O Partha, the determination of those who cannot conquer sleep, fear, lamentation, misery and pride is in the mode of ignorance.
O best of the Bharata Dynasty, now hear from Me about the three types of happiness. Happiness that leads to the end of all suffering is in the mode of goodness. Such happiness tastes bitter in the beginning, but is nectar at the end because it awakens one to self-realization.
Happiness that is born from contact between the senses and sense-objects and is like nectar in the beginning but bitter in the end is known to be in the mode of passion.
Happiness that arises from sleep, laziness and delusion and is self-deceptive in both the beginning and the end is considered to be happiness in the mode of ignorance.
There is no living being, neither on earth nor amongst the celestial beings, that is free from these three modes of material nature.
O conqueror of the enemy, O Arjuna, know that brahmanas, kshatriyas, vaishyas and shudras are classified according to the quality of their work in the three modes of material nature.