Guru Nanak, the founder of Sikhism, laid the foundation for the religion by spreading the message of one God and equality among all people. He also established the concept of the Guru, a spiritual teacher who guides and enlightens their followers. The teachings and principles of Guru Nanak were compiled and passed down by his successors, known as the ten Gurus, until the final Guru, Guru Gobind Singh, declared the Guru Granth Sahib as the eternal and living Guru of the Sikhs.

The Guru Granth Sahib, also known as the Adi Granth, is a sacred scripture that serves as the central religious text in Sikhism. It is a collection of hymns, prayers, and writings from the ten Gurus, as well as other saints and poets from various religions and backgrounds. The compilation of the Guru Granth Sahib was completed by the fifth Guru, Guru Arjan Dev, in 1604.

The importance of the Guru Granth Sahib in Sikhism is immense. It is not only considered the spiritual and philosophical guide for Sikhs, but it also serves as the living embodiment of the ten Gurus. The Guru Granth Sahib is treated with utmost respect and reverence, and it is considered a living entity that provides guidance and enlightenment to its followers.

One of the key teachings of the Guru Granth Sahib is the concept of Ik Onkar, meaning "One God." This concept emphasizes the belief in one universal, formless, and omnipotent God, who is the creator and sustainer of all things. The Guru Granth Sahib also teaches the importance of living a morally upright life, treating all people with equality and respect, and practicing selfless service to others.

The Guru Granth Sahib is also an essential part of the daily life of a Sikh. It is recited and sung in the Gurdwara (Sikh place of worship) during congregational prayers, known as Kirtan. The Guru Granth Sahib is also present at all Sikh ceremonies and is considered a witness to the rituals and vows taken by the Sikhs.

The Guru Granth Sahib is also a source of comfort and solace for Sikhs. Its hymns and prayers provide guidance and strength during difficult times, and its teachings promote inner peace and contentment. The Guru Granth Sahib also serves as a source of inspiration for Sikhs to lead a life of compassion, humility, and devotion.

In conclusion, the Guru Granth Sahib holds immense importance in Sikhism as it is considered the eternal and living Guru of the Sikhs. Its teachings and principles serve as a guide for Sikhs to lead a life of spiritual and moral excellence. The Guru Granth Sahib is a testament to the universal message of love, unity, and equality that Guru Nanak spread during his lifetime.