The niyamas form the second part of the Ashtanga path of yoga and consist of self-discipline and rules necessary for spiritual growth and personal development. The Maharishi Patanjali has outlined five niyamas to be observed, including cleanliness (saucha), contentment (santosha), austerity (tapa), introspection and study of scriptures (svadhyaya), and surrender to God (Ishvara Pranidhana).
According to our book “Decoding Patanjali’s Yoga Sutras: A Beginner’s Guide to the Ultimate Truth” by Kaushal Kumar and Jay Singhania highlights Niyama in the following way:

शौचसंतोषतपःस्वाध्यायेश्वरप्रणिधानानि नियमाः ॥३२॥
śaucasaṃtoṣatapaḥsvādhyāyeśvarapraṇidhānāni niyamāḥ

शौच-संतोष-तपः-स्वाध्याय-ईश्वर-प्रणिधानानि नियमाः​ – śauca-saṃtoṣa-tapaḥ-svādhyāya-īśvara-praṇidhānāni niyamāḥ

Sauca (shaucha)- cleanliness;
Saṃtoṣa (santosha)- contentment;
Tapaḥ (tapa)- askesis; svādhyāya (svadhyaya)- introspection, to read scriptures;
Iśvara (ishvara)- God; praṇidhānāni (pranidhana)- surrender;
Niyamāḥ (niyama)- rules;

The Maharishi has given five parts to niyama (rules): cleanliness (shaucha), contentment (santosha), askesis (tapa), introspection and reading scriptures (svadhyaya), and surrendering to God (ishvara pranidhana).

Shaucha (cleanliness):

‘Shaucha’ means ‘cleanliness’ or ‘purity’. This can be divided into ‘external’ and ‘internal’. External cleanliness means keeping your body, clothes and house clean. Eating satvik or light food is also external cleanliness. Not consuming meat, eggs, fish, alcohol, etc., is also included in external cleanliness. Keeping the mind pure is internal cleanliness. Keeping the Chitta content, energetic and away from narcissism, attachment, jealousy, lust, anger and ego is included in internal cleanliness. All the things that make the mind pure—contemplation, rumination, introspection, japa (repetition), meditation, surrender, complete absorption in one object, friendliness, compassion, happiness and disregard—are practices of internal cleanliness.

Santosha (contentment):

‘Santosh’ means ‘contentment’, ‘satisfaction’, ‘non-greediness’, etc. The subsistence of life through natural means and not desiring anything more is contentment. Discontentment is a big blockage in the path of yoga. This does not allow the mind to be stable. Therefore, the practice of contentment is necessary.

Tapa (askesis):

Tapa or askesis refers to enduring duality, which means enduring a pair of opposite qualities such as hot-cold, good-bad, up-down, profit-loss, and so on, without getting affected by them. Practising tapa is essential for eliminating the rajas and tamas impurities and cannot be established in yoga without its practice. Many people consider physical practices like fasting for months, standing or lying in water (jalashayana), keeping hands raised for days (urdhvabāhu), remaining standing for days (khaḍeś‍varī), staying in cold weather without clothes, lying under a blanket in extremely hot weather, etc., as tapa. However, in reality, tapa is a mental activity and not a physical one. Taking a powerful vow to maintain traits such as truthfulness, non-violence, restraint of the senses, non-hoarding, and not stealing is tapa. Enduring states such as favourable-unfavourable, profit-loss, hunger-thirst, and respect-disrespect with equanimity is also tapa. This helps in getting rid of impurities in the body, senses, and mind.

Svadhyaya (introspection and reading scriptures):

Svadhyaya refers to introspection and reading of scriptures. The term ‘svadhyaya’ is derived from the words ‘sva’ and ‘adhyaya’, where ‘sva’ means ‘one’s own soul’, and ‘adhyaya’ means ‘knowledge’ or ‘observation’. Therefore, svadhyaya refers to studying and observing one’s own self. Those who seek spiritual growth must introspect daily and strive to eliminate any faults they find within themselves.
Additionally, svadhyaya also involves studying scriptures that lead to liberation. Reflecting upon such texts helps in detaching oneself from worldly impurities, and strengthens the feeling of detachment in the mind.

Ishvara pranidhana (surrendering to God):

The term ‘pranidhana’ signifies surrender or devotion, and it consists of ‘pra’ meaning ‘very much’ or ‘complete’, ‘ni’ meaning ‘shelter’ or ‘refuge’, and ‘dhana’ meaning ‘place’ or ‘base’. Therefore, ‘pranidhana’ implies complete surrender to a base. Surrendering all of one’s karma to the supreme God is known as Ishvara pranidhana.
According to Yoga Philosophy, God is always liberated, is the guru of all gurus, and is unique. One of His names is Om, and by repeating His name along with understanding the meaning of God’s form, the Chitta becomes pure, and the practitioner achieves samadhi According to Sanskrit dictionaries, ‘pranidhana’ can mean to use, to appoint, behaviour, utilize, great effort, energy, religious rumination, emotional thinking, equality, renouncing the fruit of action, and more. Hence, ‘Ishvara pranidhana’ means to surrender one’s actions and the fruits of their actions to God or to be fully devoted to God.