Why and how do Sikhs bow before Sri Guru Granth Sahib Ji?

There is no difference between the Order and Word of God and God Himself. The Guru is not a physical body made of the five element, i.e. flesh & blood or ink and paper. Guru Nanak Sahib Ji was asked by Sidhs (mystics) living in the Himalayas, “Who is your Guru and who’s disciple are you?” The Guru replied:

ਸਬਦੁ ਗੁਰੂ ਸੁਰਤਿ ਧੁਨਿ ਚੇਲਾ ॥
“The Shabad is the Guru, upon whom I lovingly focus my consciousness; I am the chaylaa, the disciple.”
(Ang 943)

The Shabad, the Divine Infinite Wisdom, is the Guru. The Guru is not physical but was manifested and revealed through a body. The body is praise-worthy and respect-worthy as it contained the Divine Light, lived the message and interpreted the Shabad.

Bowing to Sri Guru Granth Sahib jee is a sign of submission before the Word of God. It is not worshipping the physical body, be it the Granth (Scripture) form now or when Guru Sahib was in human form the human body, it is a submission to the Shabad (the Divine Infinite Wisdom).

If there was a Granth with identical physical characteristics as Sri Guru Granth Sahib jee, a Sikh would not bow to it because it does not have the Shabad. Idol worship can only be true if there is in fact an idol. What is being worshipped is the Shabad, which is the revealed Order/Instructions/Word of God and that which offers enlightenment. The Shabad is by no means an idol. Therefore, bowing before the ‘Spoken revealed Word’ of God and submitting to God’s Order is in fact bowing to God.

When bowing to Sri Guru Granth Sahib Ji the seeker stands in front of the True Guru with both hands folded and offers his or her prayer and obeisence. Afterwards they place both hands flat down along with their forehead and two knees down on the floor and submit themselves before the Shabad Guru. Afterwards one circumbulates around Sri Guru Granth Sahib to express total submission and that the Guru is the centre of their lives and finishes by saying the Guru’s greeting of “Waheguru Jee Ka Khalsa, Waheguru Jee Kee Fateh” in their mind to the Guru and then to the Sangat and the Guru Roop Khalsa.

When we bow placing our forehead to the ground at the feet of the Guru, we express that we are submitting our destiny in the hands of the Guru. Bowing down before the Guru is an expression of our love and submission to Guru Ji, which is not merely a physical act, but involves humbling the mind and lowering our intellect infront of the Guru.