Shri Nanak Dev ji was born on Vikrami Samvat 1526 (1469 A.D.) Kartik Shukl Poornima in a Hindu family of Shri Kalu Ram Mehta (Kshatriya) from the holy womb of mother Shrimati Tripta Devi in a village named Talwandi of District Lahore in West Pakistan. He had read Farsi (Persian), Punjabi, Sanskrit languages. He used to study Shrimad Bhagavad Gita ji from Pandit Shri Brijlal. Shri Nanak Dev ji had two sons named Shri Chand and Lakhmi Chand.
Shri Nanak ji used to work in the store of the Nawab of Sutanpur by the grace of his brother-in-law Shri Jairam ji in the town of in-laws of his sister Nanaki. He had boundless love in God because this pious soul had done holy bhakti of Brahm God (Kaal) through the ages. In Satyayug this very Nanak ji was King Ambreesh and used to do Brahm-bhakti considering Vishnu ji as his deity. Great ascetic sage like Durvasa accepting defeat had gone in his kingdom to seek forgiveness.
In Treta Yug, the soul of Shri Nanak ji became King Janak Videhi, who came to be known as Sita ji’s father. Sage Sukhdev who was son of Great sage Vedvyaas used to fly in the sky with his supernatural power, but had not taken initiation from a Guru. When Sukhdev went to the Heaven of Vishnulok, he was returned because of not having a Guru. By the order of Vishnu ji, he made King Janak his Guru and then obtained a place in Heaven. (This is evident in Bhai Bale Wali Janam Sakhi Guru Nanak Dev Ji, Pran Sangli and Kabir Sagar)
Then in Kalyug, the soul of this very King Janak took birth in a Hindu family of Shri Kaluram Mehta (Kshatriya) and was named Shri Nanak.
“Jeevan Das Guru Saahibaan”, Page no. 42 to 44 (Writer – Sodi Teja Singh ji) – (Publisher – Chatar Singh Jeevan Singh)
As it is excerpt from “Jeevan Das Guru Saheb”
Every morning Guru ji used to go for bath in River Bein, which used to flow near the city Sultanpur. One day when you plunged into water, you did not come out. After some time, your servant, who holding clothes was sitting on the bank of the river, went home and gave the news to Jai Ram ji that Nanak ji has drowned. Then Jai Ram ji went to the river taking along the divers. They searched a lot for you, but you were not found. After searching a lot, everybody returned to their homes.
Great concern and distress was being expressed at Brother Jai Ram ji’s house, when on the third day in the morning only, a devotee taking bath came home and told sister that your brother is sitting on the bank of the river. On hearing this, Brother Jai Ram ji ran towards Bein, and as the news spread many more people also arrived there. When in this way you were surrounded by people, you quietly reached your shop. A crowd of women and men started coming at the shop with you. On seeing the crowd, Guru ji opened the door of the store, and said whatever one needs may take it. After getting the store plundered, Guru ji wearing the attire of a Fakir went and sat in a graveyard. When the Nawab got the news of plundering of the store and departure of Guru ji, he sent for Jai Ram and got the account of the books inquired by the clerk. After seeing the accounts, the clerk told that the government owes Rs 760 to Guru ji. On hearing this the Nawab became very happy. He called for Guru ji and said that don’t be upset. Taking your balance amount continue the job of store. But Guru ji said that now I will not do this job. God has ordered me to do some other job. The Nawab asked what have you been ordered? The Guru ji uttered the Mool-mantra (original mantra).
Ek Onkaar Satnaamu Karta Purkhu Nirbhau Nirvairu Akaal Moorti Ajooni Sab Guruprasaad ।
The Nawab asked that when did your God gave this order? Guru ji told that when I had gone to bathe in River Bein, I had gone to Sachkhand from there to my Lord, there I was ordered that Nanak ji, you chant this mantra and by making others chant convey the people of Kalyug across. Therefore I have to now obey this order of my Master. Brother Gurdas ji writes this context in Vaar 1 paudi 24 –
Baba paidha sachkhand naunidhi naam garibi paai।।
Meaning – Baba Nanak ji went to Sachkhand. There you attained the treasure of nine riches, naam and fearlessness. Here on the bank of Bein, where Guru ji appeared after coming out of Bein, a Saint ghat by Guru and a very beautiful Gurudwara Ber Saheb has been built. On this very place Guru ji after bathing in the morning used to sit for some time in the meditation of God.
End of excerpt from book named ‘Jeevan Das Guru Saheb’